System for enriching a bodily fluid with a gas

ABSTRACT

A system utilizes an oxygenation device to generate a gas-enriched physiologic fluid and to combine it with a bodily fluid to create a gas-enriched bodily fluid. The oxygenation device may take the form of a disposable cartridge, which is placed within an enclosure. An electronic controller manages various aspects of the system, such as the production of gas-enriched fluids, flow rates, bubble detection, and automatic operation and shut down.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to gas-enriched fluidsand, more particularly, to a system that enriches a bodily fluid with agas.

[0003] 2. Background Of The Related Art

[0004] This section is intended to introduce the reader to variousaspects of art that may be related to various aspects of the presentinvention that are described and/or claimed below. This discussion isbelieved to be helpful in providing the reader with backgroundinformation to facilitate a better understanding of the various aspectsof the present invention. Accordingly, it should be understood thatthese statements are to be read in this light, and not as admissions ofprior art.

[0005] Gas-enriched fluids are used in a wide variety of medical,commercial, and industrial applications. Depending upon the application,a particular type of fluid is enriched with a particular type of gas toproduce a gas-enriched fluid having properties that are superior to theproperties of either the gas or fluid alone for the given application.The techniques for delivering gas-enriched fluids also varydramatically, again depending upon the particular type of applicationfor which the gas-enriched fluid is to be used.

[0006] Many commercial and industrial applications exist. As oneexample, beverages may be purified with the addition of oxygen andcarbonated with the addition of carbon dioxide. As another example, thepurification of wastewater is enhanced by the addition of oxygen tofacilitate aerobic biological degradation. As yet another example, infire extinguishers, an inert gas, such as nitrogen, carbon dioxide, orargon, may be dissolved in water or another suitable fluid to produce agas-enriched fluid that expands on impact to extinguish a fire.

[0007] While the commercial and industrial applications of gas-enrichedfluids are relatively well known, gas-enriched fluids are continuing tomake inroads in the healthcare industry. Oxygen therapies, for instance,are becoming more popular in many areas. A broad assortment oftreatments involving oxygen, ozone, H₂O₂, and other active oxygensupplements has gained practitioners among virtually all medicalspecialties. Oxygen therapies have been utilized in the treatment ofvarious diseases, including cancer, AIDS, and Alzheimer's. Ozonetherapy, for instance, has been used to treat several million people inEurope for a variety of medical conditions including excema, gangrene,cancer, stroke, hepatitis, herpes, and AIDS. Such ozone therapies havebecome popular in Europe because they tend to accelerate the oxygenmetabolism and stimulate the release of oxygen in the bloodstream.

[0008] Oxygen is a crucial nutrient for human cells. It produces energyfor healthy cell activity and acts directly against foreign toxins inthe body. Indeed, cell damage may result from oxygen depravation foreven brief periods of time, and such cell damage can lead to organdysfunction or failure. For example, heart attack and stroke victimsexperience blood flow obstructions or divergence that prevent oxygen inthe blood from being delivered to the cells of vital tissues. Withoutoxygen, these tissues progressively deteriorate and, in severe cases,death may result from complete organ failure. However, even less severecases can involve costly hospitalization, specialized treatments, andlengthy rehabilitation.

[0009] Blood oxygen levels may be described in terms of theconcentration of oxygen that can be achieved in a saturated solution ata given partial pressure of oxygen (PO₂). Typically, for arterial blood,normal oxygen levels, i.e., normoxia or normoxemia, range from 90 to 110mmHg. Hypoxemic blood, i.e., hypoxemia, is arterial blood with a pO₂less than 90 mmHg. Hyperoxemic blood, i.e., hyperoxemia or hyperoxia, isarterial blood with a PO₂ greater than 400 mmHg, but less than 760 mmHg.Hyperbaric blood is arterial blood with a PO₂ greater than 760 mmHg.Venous blood, on the other hand, typically has a PO₂ level less than 90mmHg. In the average adult, for example, normal venous blood oxygenlevels range generally from 40 mmHg to 70 mmHg.

[0010] Blood oxygen levels also may be described in terms of hemoglobinsaturation levels. For normal arterial blood, hemoglobin saturation isabout 97% and varies only as pO₂ levels increase. For normal venousblood, hemoglobin saturation is about 75%. Indeed, hemoglobin isnormally the primary oxygen carrying component in blood. However, oxygentransfer takes place from the hemoglobin, through the blood plasma, andinto the body's tissues. Therefore, the plasma is capable of carrying asubstantial quantity of oxygen, although it does not normally do so.Thus, techniques for increasing the oxygen levels in blood primarilyenhance the oxygen levels of the plasma, not the hemoglobin.

[0011] The techniques for increasing the oxygen level in blood are notunknown. For example, naval and recreational divers are familiar withhyperbaric chamber treatments used to combat the bends, althoughhyperbaric medicine is relatively uncommon for most people. Sincehemoglobin is relatively saturated with oxygen, hyperbaric chambertreatments attempt to oxygenate the plasma. Such hyperoxygenation isbelieved to invigorate the body's white blood cells, which are the cellsthat fight infection. Hyperbaric oxygen treatments may also be providedto patients suffering from radiation injuries. Radiation injuriesusually occur in connection with treatments for cancer, where theradiation is used to kill the tumor. Unfortunately, at present,radiation treatments also injure surrounding healthy tissue as well. Thebody keeps itself healthy by maintaining a constant flow of oxygenbetween cells, but radiation treatments can interrupt this flow ofoxygen. Accordingly, hyperoxygenation can stimulate the growth of newcells, thus allowing the body to heal itself.

[0012] Radiation treatments are not the only type of medical therapythat can deprive cells from oxygen. In patients who suffer from acutemyocardial infarction, for example, if the myocardium is deprived ofadequate levels of oxygenated blood for a prolonged period of time,irreversible damage to the heart can result. Where the infarction ismanifested in a heart attack, the coronary arteries fail to provideadequate blood flow to the heart muscle. The treatment for acutemyocardial infarction or myocardial ischemia often involves performingangioplasty or stenting of vessels to compress, ablate, or otherwisetreat the occlusions within the vessel walls. In an angioplastyprocedure, for example, a balloon is placed into the vessel and inflatedfor a short period of time to increase the size of the interior of thevessel. When the balloon is deflated, the interior of the vessel will,hopefully, retain most or all of this increase in size to allowincreased blood flow.

[0013] However, even with the successful treatment of occluded vessels,a risk of tissue injury may still exist. During percutaneoustransluminal coronary angioplasty (PTCA), the balloon inflation time islimited by the patient's tolerance to ischemia caused by the temporaryblockage of blood flow through the vessel during balloon inflation.Ischemia is a condition in which the need for oxygen exceeds the supplyof oxygen, and the condition may lead to cellular damage or necrosis.Reperfusion injury may also result, for example, due to slow coronaryreflow or no reflow following angioplasty. Furthermore, for somepatients, angioplasty procedures are not an attractive option for thetreatment of vessel blockages. Such patients are typically at increasedrisk of ischemia for reasons such as poor left ventricular function,lesion type and location, or the amount of myocardium at risk. Treatmentoptions for such patients typically include more invasive procedures,such as coronary bypass surgery.

[0014] To reduce the risk of tissue injury that may be associated withtreatments of acute myocardial infarction and myocardial ischemia, it isusually desirable to deliver oxygenated blood or oxygen-enriched fluidsto the tissues at risk. Tissue injury is minimized or prevented by thediffusion of the dissolved oxygen from the blood to the tissue. Thus, insome cases, the treatment of acute myocardial infarction and myocardialischemia includes perfusion of oxygenated blood or oxygen-enrichedfluids. The term “perfusion” is derived from the French verb “perfuse”meaning “to pour over or through.” In this context, however, perfusionrefers to various techniques in which at least a portion of thepatient's blood is diverted into an extracorporeal circulation circuit,i.e., a circuit which provides blood circulation outside of thepatient's body. Typically, the extracorporeal circuit includes anartificial organ that replaces the function of an internal organ priorto delivering the blood back to the patient. Presently, there are manyartificial organs that can be placed in an extracorporeal circuit tosubstitute for a patient's organs. The list of artificial organsincludes artificial hearts (blood pumps), artificial lungs(oxygenators), artificial kidneys (hemodialysis), and artificial livers.

[0015] During PTCA, for example, the tolerable balloon inflation timemay be increased by the concurrent introduction of oxygenated blood intothe patient's coronary artery. Increased blood oxygen levels also maycause the hypercontractility in the normally perfused left ventricularcardiac tissue to increase blood flow further through the treatedcoronary vessels. The infusion of oxygenated blood or oxygen-enrichedfluids also may be continued following the completion of PTCA or otherprocedures, such as surgery, to accelerate the reversal of ischemia andto facilitate recovery of myocardial function.

[0016] Conventional methods for the delivery of oxygenated blood oroxygen-enriched fluids to tissues involve the use of blood oxygenators.Such procedures generally involve withdrawing blood from a patient,circulating the blood through an oxygenator to increase blood oxygenconcentration, and then delivering the blood back to the patient. Thereare drawbacks, however, to the use of conventional oxygenators in anextracorporeal circuit. Such systems typically are costly, complex, anddifficult to operate. Often, a qualified perfusionist is required toprepare and monitor the system. A perfusionist is a skilled healthprofessional specifically trained and educated to operate as a member ofa surgical team responsible for the selection, setup, and operation ofan extracorporeal circulation circuit. The perfusionist is responsiblefor operating the machine during surgery, monitoring the alteredcirculatory process closely, taking appropriate corrective action whenabnormal situations arise, and keeping both the surgeon andanesthesiologist fully informed. In addition to the operation of theextracorporeal circuit during surgery, perfusionists often function insupportive roles for other medical specialties to assist in theconservation of blood and blood products during surgery and to providelong-term support for patient's circulation outside of the operatingroom environment. Because there are currently no techniques available tooperate and monitor an extracorporeal circuit automatically, thepresence of a qualified perfusionist, and the cost associated therewith,is typically required.

[0017] Conventional extracorporeal circuits also exhibit otherdrawbacks. For example, extracorporeal circuits typically have arelatively large priming volume. The priming volume is typically thevolume of blood contained within the extracorporeal circuit, i.e., thetotal volume of blood that is outside of the patient's body at any giventime. For example, it is not uncommon for the extracorporeal circuit tohold one to two liters of blood for a typical adult patient. Such largepriming volumes are undesirable for many reasons. For example, in somecases a blood transfusion may be necessary to compensate for the bloodtemporarily lost to the extracorporeal circuit because of its largepriming volume. Also, heaters often must be used to maintain thetemperature of the blood at an acceptable level as it travels throughthe extracorporeal circuit. Further, conventional extracorporealcircuits are relatively difficult to turn on and off. For instance, ifthe extracorporeal circuit is turned off, large stagnant pools of bloodin the circuit might coagulate.

[0018] In addition to the drawbacks mentioned above, in extracorporealcircuits that include conventional blood oxygenators, there is arelatively high risk of inflammatory cell reaction and blood coagulationdue to the relatively slow blood flow rates and large blood contactsurface area of the oxygenators. For example, a blood contact surfacearea of about one to two square meters and velocity flows of about 3centimeters/second are not uncommon with conventional oxygenatorsystems. Thus, relatively aggressive anticoagulation therapy, such asheparinization, is usually required as an adjunct to using theoxygenator.

[0019] Finally, perhaps one of the greatest disadvantages to usingconventional blood oxygenation systems relates to the maximum partialpressure of oxygen (pO₂) that can be imparted to the blood. Conventionalblood oxygenation systems can prepare oxygen-enriched enriched bloodhaving a partial pressure of oxygen of about 500 mmHg. Thus, bloodhaving PO₂ levels near or above 760 mmHg, i.e., hyperbaric blood, cannotbe achieved with conventional oxygenators.

[0020] It is desirable to deliver gas-enriched fluid to a patient in amanner which prevents or minimizes bubble nucleation and formation uponinfusion into the patient. The maximum concentration of gas achievablein a liquid is ordinarily governed by Henry's Law. At ambienttemperature, the relatively low solubility of many gases, such as oxygenor nitrogen, within a liquid, such as water, produces a lowconcentration of the gas in the liquid. However, such low concentrationsare typically not suitable for treating patients as discussed above.Rather, it is advantageous to use a gas concentration within a liquidthat greatly exceeds its solubility at ambient temperature. Compressionof a gas and liquid mixture at a high pressure can be used to achieve ahigh dissolved gas concentration according to Henry's Law, butdisturbance of a gas-saturated or a gas-supersaturated liquid byattempts to inject it into an environment at ambient pressure from ahigh pressure reservoir ordinarily results in cavitation inception at ornear the exit port. The rapid evolution of bubbles produced at the exitport vents much of the gas from the liquid, so that a high degree ofgas-supersaturation no longer exists in the liquid at ambient pressureoutside the high-pressure vessel. In addition, the presence of bubblesin the effluent generates turbulence and impedes the flow of theeffluent beyond the exit port. Furthermore, the coalescence of gasbubbles in blood vessels may tend to occlude the vessels and result in agaseous local embolism that causes a decrease in local circulation,arterial hypoxemia, and systemic hypoxia.

[0021] In gas-enriched fluid therapies, such as oxygen therapiesinvolving the use of hyperoxic or hyperbaric blood, delivery techniquesare utilized to prevent or minimize the formation of cavitation nucleiso that clinically significant bubbles do not form within a patient'sblood vessels. However, it should be understood that any bubbles thatare produced tend to be very small in size, so that a perfusionist wouldtypically have difficulty detecting bubble formation without theassistance of a bubble detection device. Unfortunately, known bubbledetectors are ineffective for detecting bubbles in an extracorporealcircuit for the preparation and delivery of hyperoxic or hyperbaricblood. This problem results from the fact that the size and velocity ofsome bubbles are beyond the resolution of known bubble detectors.Therefore, micro bubbles (bubbles with diameters of about 50 micrometersto about 1000 micrometers) and some macro bubbles (bubbles withdiameters greater than 1000 micrometers) may escape detection.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The foregoing and other advantages of the invention will becomeapparent upon reading the following detailed description and uponreference to the drawings in which:

[0023]FIG. 1 illustrates a perspective view of an exemplary system forproducing gas-enriched fluid;

[0024]FIG. 2 illustrates a block diagram of the system of FIG. 1;

[0025]FIG. 3 illustrates a block diagram of the host/user interface usedin the system of FIG. 1;

[0026]FIG. 4 illustrates an exemplary display;

[0027]FIG. 5 illustrates a block diagram of a blood pump system used inthe system of FIG. 1;

[0028]FIG. 6 illustrates an interlock system used in the system of FIG.1;

[0029]FIG. 7 illustrates a top view of an oxygenation device used in thesystem of FIG. 1;

[0030]FIG. 8 illustrates a cross-sectional view taken along line 8-8 inFIG. 7;

[0031]FIG. 9 illustrates a bottom view of the oxygenation device used inthe system of FIG. 1;

[0032]FIG. 10 illustrates a detailed view of a check valve illustratedin FIG. 8;

[0033]FIG. 11 illustrates a detailed view of a piston assemblyillustrated in FIG. 8;

[0034]FIG. 12 illustrates a cross-sectional view taken along line 12-12of FIG. 8;

[0035]FIG. 13 illustrates a detailed view of a valve assemblyillustrated in FIG. 8;

[0036]FIG. 14 illustrates a cross-sectional view of the valve assemblytaken along line 14-14 in FIG. 13;

[0037]FIG. 15 illustrates a detailed view of a capillary tubeillustrated in FIG. 8;

[0038]FIG. 16 illustrates a detailed view of a vent valve illustrated inFIG. 8;

[0039]FIG. 17 illustrates an exploded view of the cartridge andcartridge enclosure;

[0040]FIG. 18 illustrates a front view of the cartridge receptacle ofthe cartridge enclosure illustrated in FIG. 1;

[0041]FIG. 19 illustrates a cross-sectional view of the cartridgeenclosure taken along line 19-19 in FIG. 18;

[0042]FIG. 20 illustrates the front view of a door latch on the door ofthe cartridge enclosure;

[0043]FIG. 21 illustrates a cross-sectional view of the door latch takenalong line 21-21 in FIG. 20;

[0044]FIG. 22 illustrates another cross-sectional view of the doorlatch;

[0045]FIG. 23 illustrates a detailed view of the door latch of FIG. 19;

[0046]FIG. 24 illustrates a cross-sectional view of the door latchincluding a blocking mechanism;

[0047]FIG. 25 illustrates a cross-sectional view of the lockingmechanism of FIG. 24 as the latch is being closed;

[0048]FIG. 26 illustrates a cross-sectional view of the lockingmechanism after the latch has been closed;

[0049]FIG. 27 illustrates a bottom view of the cartridge enclosure;

[0050]FIG. 28 illustrates a cross-sectional view taken along line 28-28in FIG. 27 of a valve actuation device in an extended position;

[0051]FIG. 29 illustrates a cross-sectional view taken along line 28-28in FIG. 27 of a valve actuation device in a retracted position;

[0052]FIG. 30 illustrates a top-view of the cartridge enclosure;

[0053]FIG. 31 illustrates a cross-sectional view taken along line 31-31of FIG. 30 of a valve actuation device in its extended position;

[0054]FIG. 32 illustrates a cross-sectional view taken along line 31-31of FIG. 30 of a valve actuation device in its retracted position;

[0055]FIG. 33 illustrates a cross-sectional view of the cartridgeenclosure taken along line 33-33 in FIG. 18;

[0056]FIG. 34 illustrates a detailed view of an ultrasonic sensorillustrated in FIG. 33;

[0057]FIG. 35 illustrates a detailed view of an ultrasonic sensorillustrated in FIG. 33;

[0058]FIG. 36 illustrates a top view of the cartridge enclosureincluding gas connections;

[0059]FIG. 37 illustrates a cross-sectional view taken along line 37-37in FIG. 36;

[0060]FIG. 38 illustrates a detailed view of the cross-sectional view ofFIG. 37 of a gas connection in an unseated position;

[0061]FIG. 39 illustrates a detailed view of the cross-sectional view ofFIG. 37 of a gas connection in a seated position;

[0062]FIG. 40 illustrates a partial cross-sectional view of a drivemechanism;

[0063]FIGS. 41A and B illustrate an exploded view of the drive mechanismillustrated in FIG. 40;

[0064]FIG. 42 illustrates a cross-sectional view taken along line 42-42in FIG. 40;

[0065]FIG. 43 illustrates a detailed view of the load cell illustratedin FIG. 42;

[0066]FIG. 44 illustrates an exploded view of a sensor assembly of thedrive mechanism;

[0067]FIG. 45 illustrates a top partial cross-sectional view of thedrive assembly;

[0068]FIG. 46 illustrates a cross-sectional view taken along line 46-46of FIG. 45;

[0069]FIG. 47 illustrates a detailed view of a portion of the sensorassembly illustrated in FIG. 46;

[0070]FIG. 48 illustrates an exemplary sensor for use in the sensorassembly illustrated in FIG. 44;

[0071]FIG. 49 illustrates a state diagram depicting the basic operationof the system illustrated in FIG. 1;

[0072]FIG. 50 illustrates a block diagram of a system controller;

[0073]FIG. 51 illustrates a block diagram of a bubble detector;

[0074]FIG. 52 illustrates an exemplary signal transmitted by the bubbledetector;

[0075]FIG. 53 illustrates an exemplary signal received by the bubbledetector;

[0076]FIG. 54 illustrates a bubble sensor coupled to the return tube;

[0077]FIG. 55 illustrates a cross-sectional view of the return tube ofFIG. 54;

[0078]FIG. 56 illustrates a schematic diagram of a system used toevaluate bubble detectors, such as the bubble detector of the presentsystem;

[0079]FIG. 57 illustrates an elevated side view of an exemplarycapillary tube;

[0080]FIG. 58 illustrates a side view of the capillary tube of FIG. 57positioned within a connecting device incident to a material flow;

[0081]FIG. 59 illustrates a schematic diagram of an alternative systemused to evaluate bubble detectors, where the system includes a pulsedampener;

[0082]FIG. 60 illustrates a detailed view of an exemplary pulsedampener, and FIG. 61 illustrates the output of a digital signalprocessor indicating the diameters of bubbles detected by the bubbledetector.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[0083] One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, as in any engineering or designproject, numerous implementation-specific decisions must be made toachieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

[0084] System Overview

[0085] Turning now to the drawings, and referring initially to FIG. 1, asystem for preparing and delivering gas-enriched fluid is illustratedand designated by a reference numeral 10. Although the system 10 may beused to prepare a number of different types of gas-enriched fluids, inthis particular example, the system 10 prepares oxygen-enriched enrichedblood. As will be described in detail herein, the system 10 is adaptedto withdraw blood from a patient, combine the blood with aoxygen-supersaturated physiologic fluid, and deliver the oxygen-enrichedblood back to the patient.

[0086] Because the system 10 may be used during surgical procedures, itis typically sized to be placed within a normal operating roomenvironment. Although the system 10 may be configured as a stationarydevice or a fixture within an operating room, it is often desirable forvarious surgical devices to be mobile. Accordingly, in this example, thesystem 10 is illustrated as being coupled to a rolling base 12 via apedestal 14. Although some of the electrical and/or mechanicalcomponents of the system 10 may be housed in the base 12 or the pedestal14, these components will more typically be placed within a housing 16.To facilitate positioning of the system 10, a handle 18 may be coupledto the housing 16 for directing movement of the system 10, and a pedal20 may be coupled to the base 12 for raising and lowering the housing 16on the pedestal 14 (via a rack and pinion mechanism which is not shown,for instance).

[0087] The housing 16 may include a cover, such as a hinged door 22, forprotecting certain components of the system 10 that are positioned inlocations external to the housing 16. Components that are typicallylocated on the exterior of the housing 16 may include a blood pump 24, acartridge enclosure 26, as well as various control devices 28.Additional external items may include a user interface panel 30 and adisplay 32.

[0088] Referring now to FIG. 2, a block diagram representing variouscomponents of the system 10 is illustrated. An appropriate draw tube 34,such as a cannula or catheter, is inserted into an appropriate bloodvessel 36 of a patient 38. Blood is drawn from the patient 38 throughthe draw tube 34 using the blood pump system 24. Specifically, the bloodpump system 24 includes a pump 40, such as a peristaltic pump. As theperistaltic pump 40 mechanically produces waves of contraction along theflexible tube 34, fluid within the tube 34 is pumped in the direction ofthe arrow 42. As will be discussed in detail below, the blood pumpsystem 24 includes a flow meter 46 that receives feedback from a flowprobe 48. The flow probe 48 is coupled to the patient's return tube 50,such as a cannula or catheter. With this feedback, the blood pump system24 can operate as an automatic extracorporeal circuit that can adjustthe r.p.m. of the peristaltic pump 40 to maintain the desired bloodflow.

[0089] The draw tube 34 and/or the return tube 50 may be sub-selectivecatheters. The construction of the return tube 50 may be of particularimportance in light of the fact that the gas-enriched bodily fluid maybe gas-saturated or gas-supersaturated over at least a portion of thelength of the return tube 50. Therefore, the return tube 50, inparticular, is typically designed to reduce or eliminate the creation ofcavitation nuclei which may cause a portion of the gas to come out ofsolution. For example, the length-to-internal diameter ratio of thecatheter may be selected to create a relatively low pressure drop fromthe oxygenation device 54 to the patient 38. Typically, the catheter issized to fit within a 6 french guide catheter. Materials such aspolyethylene, PEBAX (polyetheramide), or silicone, for example, may beused in the construction of the catheter. Also, the lumen of thecatheter should be relatively free of transitions that may cause thecreation of cavitation nuclei. For example, a smooth lumen having nofused polymer transitions typically works well.

[0090] The blood is pumped through the draw tube 34 in the direction ofthe arrow 52 into an oxygenation device 54. Although various differenttypes of oxygenation devices may be suitable for oxygenating thepatient's blood prior to its return, the oxygenation device 54 in thesystem 10 advantageously prepares an oxygen-supersaturated physiologicfluid and combines it with the blood to enrich the blood with oxygen.Also, the oxygenation device 54 is advantageously sterile, removable,and disposable, so that after the procedure on the patient 38 has beencompleted, the oxygenation device 54 may be removed and replaced withanother oxygenation device 54 for the next patient.

[0091] Advantages of the oxygenation device 54 will be described ingreat detail below. However, for the purposes of the discussion of FIG.2, it is sufficient at this point to understand that the physiologicfluid, such as saline, is delivered from a suitable supply 56, such asan IV bag, to a first chamber 58 of the oxygenation device 54 under thecontrol of a system controller 55. A suitable gas, such as oxygen, isdelivered from a supply 60, such as a tank, to a second chamber 62 ofthe oxygenation device 54. Generally speaking, the physiologic fluidfrom the first chamber 58 is pumped into the second chamber 62 andatomized to create a oxygen-supersaturated physiologic solution. Thisoxygen-supersaturated physiologic solution is then delivered into athird chamber 64 of the oxygenation device 54 along with the blood fromthe patient 38. As the patient's blood mixes with theoxygen-supersaturated physiologic solution, oxygen-enriched blood iscreated. This oxygen-enriched blood is taken from the third chamber 64of the oxygenation device 54 by the return tube 50.

[0092] A host/user interface 66 of the system 10 monitors both thepressure on the draw tube 34 via a draw pressure sensor 68 and thepressure on the return tube 50 via a return pressure sensor 70. Asillustrated in FIG. 6, the ends of the draw tube 34 and the return tube50 that couple to the oxygenation device 54 are embodied in aY-connector 71 in this example. The Y-connector 71 includes the drawpressure sensor 68 and the return pressure sensor 70, which areoperatively coupled to the host/user interface 66 via an electricalconnector 73. The host/user interface 66 may deliver these pressurereadings to the display 32 so that a user can monitor the pressures andadjust them if desired. The host/user interface 66 also receives asignal from a level sensor 72 that monitors the level of fluid withinthe mixing chamber 64 of the oxygenation device 54 to ensure that theoxygen-supersaturated physiological solution is mixing with thepatient's blood with little or no bubble formation.

[0093] The system 10 further advantageously includes a suitable bubbledetector 74. The bubble detector 74 includes a suitable bubble sensor 76positioned at the return tube 50 to detect bubbles as they pass throughthe return tube 50 to the patient 38. Again, as discussed in greaterdetail below, the bubble detector 74 receives the signals from thebubble sensor 76 and processes information regarding the nature of anybubbles that may be traveling in the oxygen-enriched blood going back tothe patient 38. In this embodiment, the bubble detector 74 provides thisinformation to the host/user interface 66 so that information regardingbubbles in the effluent may be provided to the user via the display 32.The bubble detector 74 may also control or shut down the system 10 incertain circumstances as discussed in detail below.

[0094] The system 10 also includes an interlock system 44. The interlocksystem 44 communicates with many of the components of the system 10 forvarious reasons. The interlock system 44 monitors the various componentsto ensure that the system 10 is operating within certain prescribedbounds. For example, the interlock system 44 receives informationregarding draw and return pressures from the pressure sensors 68 and 70,information regarding fluid level in the mixing chamber 64 from thelevel sensor 72, and information regarding the number and/or size ofbubbles from the bubble detector 74, as well as other informationregarding the operating states of the various components. Based on thisinformation, the interlock system 44 can shut down the system 10 shouldit begin to operate outside of the prescribed bounds. For example, theinterlock system 44 can engage clamps 78 and 80 on the draw tube 34 andthe return tube 50, respectively, as well as disable the blood pumpsystem 24 and the system controller 55 that controls the oxygenationdevice 54. While the interlock system 44 typically operates in thisautomatic fashion, a safety switch 82 may be provided so that a user caninitiate a shutdown of the system 10 in the same fashion even if thesystem 10 is operating within its prescribed bounds.

[0095] The system 10 has a low priming volume relative to conventionalextracorporeal circuits, typically in the range of 25 to 100milliliters. Thus, a heater typically is not used with the system 10.However, if it is desirable to control the temperature of the incomingblood in the draw tube 34 or the outgoing gas-enriched blood in thereturn tube 50, an appropriate device, such as a heat exchanger, may beoperatively coupled to one or both of the tubes 34 and 50. Indeed, notonly may the heat exchanger (not shown) be used to warm the fluid as ittravels through the system 10, it may also be used to cool the fluid. Itmay be desirable to cool the fluid because moderate hypothermia, around30° C. to 34° C. has been shown to slow ischemic injury in myocardialinfarction, for example.

[0096] Host/User Interface

[0097] The various details of the system 10 described above withreference to FIGS. 1 and 2 will be described with reference to theremaining Figs. Turning now to FIG. 3, an exemplary embodiment of thehost/user interface 66 is illustrated. The host/user interface 66includes a user interface 84 and a host interface 85. The user interface84 may include a user input and display device, such as a touch screendisplay 86. As illustrated in FIG. 4, the touch screen display 86 mayinclude “buttons” 87 that initiate certain operations when a usertouches them. The touch screen display 86 may also include informationsuch as alarms/messages 88, status indicators 89, blood flow information90, and bubble count9l.

[0098] The user inputs are handled by a touch screen driver 92, and thedisplayed information is handled by a display driver 93. The touchscreen driver 92 transmits user inputs to an interface, such as anRS-232 interface 94. The RS-232 interface 94 may communicate these userinputs to other portions of the system 10, such as the system controller55, the interlock system 44, the blood pump system 24, and the bubbledetector 74. The display driver 93 communicates with a displaycontroller 95, which is also coupled to the RS-232 interface 94 via abus 96. The display controller 95 receives updated information from thevarious other portions of the system 10, and it uses this information toupdate the display 86.

[0099] The host interface 85 may also include various othercapabilities. For example, the host interface 85 may include a soundcard 97 to drive speakers 98 on the user interface 84. In addition, anetwork adapter 99 may allow the host interface 85 to communicate withan external network, such as a LAN in the hospital or a remote networkfor providing updates for the system 10, e.g., the Internet. Finally,the host interface 85 may include an analog and/or digital I/O device101, which in this example transmits and receives certain signals suchas an enable signal, a “request to stop” signal, a draw pressure signal,and a return pressure signal.

[0100] Blood Pump System and Interlock System

[0101] Many of the components described below, while particularly usefulin the exemplary system 10, may be quite useful in other types ofsystems as well. For example, the blood pump system 24 described indetail with reference to FIG. 5 may be used not only in the context ofthe system 10, but also in other types of perfusion systems, such asconventional heart-lung machines and other types of other extracorporealcircuits. As previously discussed, the blood pump system 24 utilizes asuitable pump 40, such as a peristaltic pump, to draw blood from thepatient 38 through a draw tube 34. The blood pump system 24 furtherincludes a flow meter 46, such as a transonic flow meter, whichcommunicates with a flow transducer 48 via lines 100 and 102. Thefeedback from the transducer 48 enables the blood pump system 24 tomaintain the desired flow rate. The desired flow rate may be entered bya user, such as perfusionist or a nurse, via the control panel 30. Inthis example, the control panel 30 includes an indication of the currentblood flow rate in milliliters per minute, as well as an “up” button 104and a “down” button 106 that permit a user to adjust the blood flow rateupwardly and downwardly, respectively. The control panel 30 furtherincludes a “prime” button 108, a “start” button 110, and a “stop” button112. In addition, the control panel 30 may be augmented by a foot switch114, which includes a stop pedal 116, which performs the same functionas the stop button 112, and a prime start pedal 118, which performs thesame function as the prime button 108 and the start button 110.

[0102] Because the blood pump system 24 utilizes feedback from the flowtransducer 48 to maintain and adjust the r.p.m. of the pump 40 in amanner which provides a consistent flow rate, the blood pump system 24requires no user interaction once the system has been primed and theflow rate has been set. Therefore, unlike blood pumps used in otherextracorporeal circuits, the blood pump system 24 may be operated by asemi-skilled technician or nurse, rather than a highly skilledperfusionist.

[0103] To provide an extra measure of confidence with such semi-skilledoperation, the blood pump system 24 takes advantage of certain featuresprovided by the interlock system 44. For example, referring to theinterlock system 44 illustrated in FIG. 6 as well, the interlock system44 may include or have access to a personality module 120. Thepersonality module 120 may include a memory 122, such as a read onlymemory for example. The memory 122 of the personality module 120 mayinclude various information, such as flow rates and ranges, as well asother information to be discussed below. Therefore, for a particularpatient or for a particular type of patient, the desired flow rateand/or the desired flow rate range may be programmed into the memory122. For example, in acute myocardial infarction applications, the flowrate may be 75 milliliters per minute, or for stroke applications theflow rate may be 300 milliliters per minute. In this exemplaryembodiment, the personality module 120 may be located in the Y-connector71. Because the information programmed into the personality module 120may be related to a particular patient or a particular type of patient,and because a new Y-connector is typically used with each patient, thelocation of the personality module 120 in the Y-connector 71 provides aneffective method of customizing the system 10 with each patient treated.

[0104] The interlock system 44 reads this flow information from thememory 122 and compares it to the flow rate delivered by the flow meter46 on line 124. As long as the flow rate from the flow meter 46 ismaintained at the desired flow rate or within the desired flow rangeprogrammed into the memory 122, the interlock system 44 will continue tosupply an enable signal on line 126 to the blood pump system 24.However, should the flow rate fall outside of the desired range, due tooperator intervention, failure of the flow transducer 48, etc., theinterlock system 44 will switch the signal on the line 126 to disablethe blood pump system 24. The interlock system 44 will further actuatethe clamps 78 and 80 in order to shut down the system 10 in a mannersafe for the patient 38.

[0105] The interlock system 44 includes an analog conditioning circuit130 that receives and conditions the analog flow rate signal from theflow meter 46 on the line 124. This conditioned signal is compared withthe information from the memory 122 using comparators and thresholdsettings 132. The results of this comparison are delivered to a logicblock 134, which may be, for example, a field programmable gate array(FPGA) or a complex programmable logic device (CPLD). The logic block134 generates the enable or disable signal on the line 126.

[0106] The conditioning circuit 130 also receives the analog pressuresignals from the draw pressure transducer 68 and the return pressuretransducer 70. These pressures may be monitored to ensure that neitherthe draw tube 34 nor the return tube 50 are kinked or otherwise unableto deliver fluid at a minimum desired pressure or higher. The logicblock 134 compares these pressures to the minimum pressure setting,e.g., −300 mm Hg, and delivers a warning signal if either pressure dropsbelow the minimum pressure setting. In addition, the draw pressure ismonitored to ensure that it remains higher than a minimal draw pressurethreshold, e.g. −300 mm Hg, to ensure that bubbles are not pulled out ofsolution by the blood pump 40. Still further, the return pressure ismonitored to ensure that it does not exceed a maximum return pressure,e.g. 2000 mm Hg.

[0107] The manner in which the interlock system 44 interfaces withvarious other portions of the system 10 will be discussed below whereappropriate. However, it can be seen that the blood pump system 24 andthe interlock system 44 provide a technique by which blood may beremoved from a patient at a desired and maintainable flow rate and thatany deviation from the desired flow rate will cause the system to shutdown in a manner which is safe for the patient 38. Accordingly, the useof a perfusionist may be obviated in most circumstances.

[0108] Oxygenation Device

[0109] Although the blood pump system 24 may be used in a variety ofdifferent systems, for the primary purpose of this discussion it isincorporated within the system 10. As described in reference to FIG. 2above, one of its main purposes is to deliver blood to the oxygenationdevice 54. Accordingly, before discussing the blood pump system 24 orthe other components further, an understanding of the manner in whichthe oxygenation device 54 functions is appropriate.

[0110] Referring first to FIGS. 7, 8, and 9, an exemplary embodiment ofan oxygenation device 54 is illustrated. As mentioned previously, theoxygenation device 54 includes three chambers: a fluid supply chamber58, an atomization chamber 62, and a mixing chamber 64. Generallyspeaking, physiologic fluid, such as saline, is drawn into the fluidsupply chamber 58. The physiologic fluid is transferred under pressurefrom the fluid supply chamber 58 to the atomization chamber 62. In theatomization chamber 62, the physiologic fluid is enriched with a gas,such as oxygen, to form a gas-enriched physiologic fluid. For example,the physiologic fluid may be supersaturated with the gas. Thegas-enriched physiologic fluid is transferred to the mixing chamber 64to be combined with a bodily fluid, such as blood. The mixing of thegas-enriched physiologic fluid with the bodily fluid forms agas-enriched bodily fluid. In one example, blood from a patient is mixedwith an oxygen-supersaturated saline solution and transmitted back tothe patient.

[0111] Beginning with a detailed discussion of the fluid supply chamber58, an appropriate delivery device, such as a tube 140, is coupled to asupply of physiologic fluid. In this example, the tube 140 may include adrip chamber 141 and is coupled at one end to an IV bag 56. The otherend of the tube 140 is coupled to a nozzle 142. The nozzle 142 forms aportion of a fluid passageway 144 that leads to the fluid supply chamber58. A check valve 146 is disposed in the fluid passageway 144 so thatfluid may enter the fluid chamber 58 through the fluid passageway 144,but fluid cannot exit through the fluid passageway 144.

[0112] As illustrated by the detailed view of FIG. 10, check valve 146has an O-ring seal 148 that is disposed between a lip in the fluidpassageway 144 and the nozzle 142. A spring 150 biases a ball 152 intocontact with the O-ring seal 148. When fluid moving in the direction ofthe arrow 154 overcomes the force of the spring 150 and the pressurewithin the fluid supply chamber 58, the ball 152 is pushed against thespring 150 so that fluid may flow into the fluid supply chamber 58.However, fluid cannot flow in the opposite direction because the ball152 efficiently seals against the O-ring seal 148.

[0113] A piston assembly 160 is disposed at the opposite end of thefluid supply chamber 58. The piston assembly 160 includes a sleeve 162that is fixedly disposed within the fluid supply chamber 58. Asillustrated in greater detail in FIG. 11, a plunger 164 is slidablydisposed within the sleeve 162. A cap 166 is disposed at one end of theplunger 164. The cap includes a flange 168 that has an outer diametergreater than the inner diameter of the sleeve 162 to limit downwardmovement of the piston assembly 160. Although the sleeve 162, theplunger 164, and the cap 166 are advantageously made of a relativelyrigid material, such as plastic, a relatively resilient end piece 170 isdisposed on the cap 166. The end piece 170 advantageously includessealing members 172 that seal against the interior walls of the fluidsupply chamber 58.

[0114] As illustrated by the phantom lines in FIG. 11, the pistonassembly 160 is moveable between a first position (shown by the solidlines) and a second position (shown by the phantom lines). To facilitatethis movement, a device to be described below is coupled to the free end174 of the piston assembly 160. Although such coupling may occur invarious suitable manners, in this example a key 176 is provided at thefree end 174 of the piston assembly 160. The key 176 includes a narrowportion 178 and a relatively wider portion 180 so that it somewhatresembles a doorknob, thus allowing a device to latch onto the pistonassembly 160 and move it between the first and second positions.

[0115] As will be appreciated from a thorough study of this entirediscussion, one of the primary advantages of the particular oxygenationdevice 54 disclosed herein involves its sterility and disposability. Thesterility of the piston assembly 160 may be facilitated by providing asterility sheath 182 disposed between the cap 166 and the sleeve 162. Inthis embodiment, the sterility sheath 182 includes an extendable tube184 that is coupled to the cap 166 by a clamp 186 and coupled to theouter portion of the sleeve 162 by a clamp 188. The expandable tube 184may take various forms, such as a plastic tube that folds in anaccordion-like manner when the piston assembly 160 is in its retractedposition (as shown by the solid lines). However, the expandable tube 184may take various other forms, such as a flexible member that stretchesbetween the retracted position and the extended position of the pistonassembly 160. The clamps 186 and 188 may also take various suitableforms, such as rubber O-rings in this example.

[0116] Referring additionally to FIG. 12, the fluid supply chamber 58further includes a second fluid passageway 190. As illustrated by way ofa specific example in the present embodiment, the fluid passageway 190is coupled to a fluid passageway 194 by a tube 196. The passageway 194is an inlet to a valve assembly 200 that controls the manner in whichfluid from the fluid supply chamber 58 is delivered into the atomizationchamber 62.

[0117] In operation, the piston assembly 160 within the fluid supplychamber 58 acts as a piston pump. As the piston assembly 160 retracts,fluid is drawn into the chamber 58 from the fluid supply 56. No fluidcan be drawn from passageway 190 because valve assembly 200 is closedand a check valve 192 is closed in this direction. As the pistonassembly 160 extends, the fluid within the chamber 58 is pressurized,typically to about 670 psi, and expelled from the fluid supply chamber58 through the fluid passageway 190. The outlet of the fluid supplychamber 58 is coupled to an inlet of the atomization chamber 62 via anappropriate fluid passageway.

[0118] Detailed views of the valve assembly 200 are illustrated in FIGS.13 and 14. The valve assembly 200 includes three valves: a fill valve202, a flush valve 204, and a flow valve 206. While any suitable valvearrangement and type of valve may be used, in this embodiment the valves202, 204, and 206 are needle valves that are normally biased in theclosed position as shown. When the pressure within the atomizationchamber 62 rises above a certain level, such as about 100 psi, thevalves 202, 204, and 206 will move from the closed position to theopened position, assuming that they are allowed to do so. In thisembodiment, as will be discussed in greater detail below, push pins andassociated actuation mechanisms (as illustrated by the phantom lines inFIG. 13) maintain the valves 202, 204, and 206 in the closed positionsuntil one or more of the valves 202, 204, and 206 is to be opened.

[0119] Gas, such as oxygen, is delivered under pressure to theatomization chamber 62 via a passageway 210. For example, the oxygentank 60 may be coupled to the inlet of the passageway 210 to provide thedesired oxygen supply. If all of the valves 202, 204, and 206 areclosed, fluid flows from the inlet passageway 194 into a passageway 212in which the fill valve 202 is located. Because the cross-sectional areaof the passageway 212 is larger than the cross-sectional area of thefill valve 202, the fluid flows around the closed fill valve 202 andinto a passageway 214 that leads to an atomizer 216.

[0120] The atomizer 216 includes a central passageway 218 in which aone-way valve 220 is disposed. In this embodiment, the one-way valve 220is a check valve similar to that described with reference to FIG. 10.Accordingly, when the fluid pressure overcomes the force of the springin the one-way valve 220 and overcomes the pressure of the gas withinthe atomizer chamber 62, the fluid travels through the passageway 218and is expelled from a nozzle 222 at the end of the atomizer 216.

[0121] The nozzle 222 forms fluid droplets into which the oxygen withinthe atomization chamber 62 diffuses as the droplets travel within theatomization chamber 62. This oxygen-enriched fluid may be referred toherein as aqueous oxygen (AO). In this embodiment, the nozzle 222 formsa droplet cone defined by the angle α, which is typically about 20degrees to about 40 degrees at normal operating pressures, e.g., about600 psi, within the atomization chamber 62. The nozzle 222 is asimplex-type, swirled pressurized atomizer nozzle including a fluidorifice of about 0.004 inches diameter to 0.005 inches diameter. Itshould be appreciated that the droplets infused with the oxygen fallinto a pool at the bottom of the atomizer chamber 62. Since the atomizer216 will not atomize properly if the level of the pool rises above thelevel of the nozzle 222, the level of the pool is controlled to ensurethat the atomizer 216 continues to function properly.

[0122] The oxygen is dissolved within the atomized fluid to a muchgreater extent than fluid delivered to the atomizer chamber 62 in anon-atomized form. As previously stated, the atomizing chamber typicallyoperates at a constant pressure of about 600 psi. Operating the atomizerchamber 62 at 600 psi, or any pressure above 200 psi, advantageouslypromotes finer droplet formation of the physiologic solution from theatomizer 216 and better saturation efficiency of the gas in thephysiologic fluid than operation at a pressure below 200 psi. As will beexplained shortly, the oxygen-supersaturated fluid formed within theatomizer chamber 62 is delivered to the mixing chamber 64 where it iscombined with the blood from the patient 38. Because it is desirable tocontrol the extent to which the patient's blood is enriched with oxygen,and to operate the system 10 at a constant blood flow rate, it may bedesirable to dilute the oxygen-supersaturated fluid within the atomizerchamber 62 to reduce its oxygen content. When such dilution is desired,the fill valve 202 is opened to provide a relatively low resistance pathfor the fluid as compared to the path through the atomizer 216.Accordingly, instead of passing through the atomizer 216, the fluidflows through a passageway 230 which extends upwardly into the atomizerchamber 62 via a tube 232. The tube 232 is advantageously angledsomewhat tangentially with respect to the cylindrical wall of theatomizer chamber 62 so that the fluid readily mixes with theoxygen-supersaturated fluid in the pool at the bottom of the atomizerchamber 62.

[0123] The valve assembly 200 essentially performs two additionalfunctions. First, with the fill valve 202 and the flow valve 206 closed,the flush valve 204 may be opened so that fluid flows from the inletpassageway 194, through the passageways 212 and 214, and intopassageways 240 and 242, the latter of which has a cross-sectional arealarger than the cross-sectional area of the flow valve 206. Thus, thefluid flows out of an outlet passageway 244 that is coupled to acapillary tube 246. The capillary tube 246 terminates in a tip 248 thatextends upwardly into the mixing chamber 64. Since this fluid has notbeen gas-enriched, it essentially serves to flush the passageways 242and 244, and the capillary tube 246 to remove any contaminants and toensure adequate fluid flow. Second, with the fill valve 202 and theflush valve 204 closed, the flow valve 206 may be opened when it isdesired to deliver the gas-supersaturated fluid from the pool at thebottom of the atomizer chamber 62 into the mixing chamber 64.

[0124] In this second circumstance, the gas-supersaturated fluid readilyflows from the atomization chamber 62 through the capillary tube 246 andinto the mixing chamber 64 due to the fact that pressure within theatomization chamber 62 is relatively high, e.g., approximately 600 psi,and pressure within the mixing chamber 64 is relatively low, e.g., about30 psi. The end of the capillary tip 248 is advantageously positionedbelow a blood inlet 250 of the mixing chamber 64. This spacialarrangement typically ensures that the blood flowing through the drawtube 34 and into the blood inlet 250 effectively mixes with theoxygen-supersaturated fluid flowing into the mixing chamber 64 throughthe capillary tip 248. Finally, by the force of the blood pump system24, the oxygenated blood is pumped out of the mixing chamber 64 throughan outlet 252 into the return tube 50.

[0125] Typically, the capillary tube 246 and the capillary tip 248 arerelatively long to ensure that proper resistance is maintained so thatthe oxygen within the oxygen-supersaturated fluid remains in solution asit travels from the atomization chamber 62 into the mixing chamber 64.For example, the capillary tube 246 and the tip 248 may be in the rangeof 50 microns to 300 microns in length and in the range of 3 inches to20 inches in internal diameter. To maintain the compact size of theoxygenation device 54, therefore, the capillary tube 246 is wrappedabout the exit nozzle 252 of the mixing chamber 64, as illustrated inthe detailed drawing of FIG. 15. To protect the coiled capillary tube246 from damage, a protective shield 254 is advantageously formed aroundthe coiled capillary tube 246 to create a compartment 256.

[0126] Both the atomization chamber 62 and the mixing chamber 64 includevent valves 258 and 260, respectively. The vent valves 258 and 260, asillustrated in the detail drawing of FIG. 16, are one-way valves thatallow gas pressure to be vented out of the oxygenation device 54 andinto the atmosphere. In this particular embodiment, the vent valves 258and 260 include a plunger 262 that is biased in a closed positionagainst an O-ring seal 264 by a spring 266. The biasing force is lightso that only one to two psi within the respective chambers 62 or 64 issufficient to move the plunger 262 away from the seal 264 to vent thechamber. Therefore, as will be discussed in greater detail below,actuation devices that are part of the cartridge enclosure 26 andcontrolled by the system controller 55 normally maintain the valves 258and 260 in the closed position.

[0127] Before beginning a discussion of the remainder of the system 10,a few points regarding oxygenation of blood in general, and the use ofthe disclosed oxygenation device 54 in particular, should be noted.First, various methods of oxygenating blood are known or underdevelopment. Although an atomizing chamber provides a convenientmechanism for diffusing relatively large amounts of gas into a fluid ina relatively short period of time, it is not the only way of dissolvinggas within a fluid. Indeed, other devices, such as membrane oxygenators,gas spargers, bubblers, and thin film oxygenation devices, may be usedto perform this function as well. Second, although a piston pumpsimilarly provides a compact and efficient method of pressurizing fluidprior to sending it to an oxygenator, such as the atomizer, other typesof pumps or methods of pressurization may be used as well. Third,although a mixing chamber provides a compact environment in which themixing of the gas-supersaturated fluid with blood may be appropriatelymonitored and controlled, gas-enriched fluid may be mixed with blood inother ways. For example, gas-supersaturated fluid may be mixed withblood within the mixing zone of a catheter or other suitable device.Therefore, although a piston pump, atomizer, and mixing chamber comprisethe oxygenation device 54 utilized in the exemplary embodiment of thesystem 10, due to certain perceived advantages, other devices can,generally speaking, perform these functions.

[0128] With these generalities in mind, the oxygenation device 54disclosed herein offers several advantages that make it particularlyattractive for use within a medical environment. First, the oxygenationdevice 54 is advantageously made from a clear plastic, such aspolycarbonate which can be molded to provide a high strength, low costdevice. Second, the oxygenation device 54 is relatively compact, with anexemplary specimen measuring approximately 12 cm in height, 10 cm inwidth, and 5.5 cm in depth. Thus, it can be utilized within a system 10that fits easily within an operating room or special procedures lab,regardless of whether the system 10 is fixed or mobile. Third, theoxygenation device 54 combines the preparation of the oxygen-enrichedfluid, along with the mixing of the oxygen-enriched fluid with theblood, into a unitary device utilizing only four connections: (1) fluidsupply, (2) oxygen supply, (3) blood supply, and (4) blood return. Theother connections are part of the oxygenation device 54 itself, and theyrequire no additional connection from the user. Fourth, all of thevalves used to operate the oxygenation device 54 are integrated withinits unitary structure. Thus, the valves and their associated fluidpassageways are protected against external contamination, and users areprotected against any contamination that may arise from the use of thevarious fluids as well. As a result, the oxygenation device 54 is arelatively contamination-free cartridge that may be used during asurgical procedure on a patient, and then removed and replaced prior toperforming a surgical procedure on the next patient.

[0129] Cartridge Enclosure

[0130] Prior to discussing the remainder of the electrical componentsand the manner in which they control the various mechanical componentsof the system 10, the manner in which certain mechanical componentsinterface with the oxygenation device 54 will now be discussed. Asmentioned previously, the oxygenation device 54 is placed inside of thecartridge enclosure 26. FIG. 17 illustrates an exploded view of thecartridge enclosure 26, and FIG. 18 illustrates a front view of thecartridge enclosure 26. In this embodiment, the cartridge enclosure 26includes a cartridge receptacle 302 that is accessed by a hinged door304. When the oxygenation device 54 is placed within the cartridgereceptacle 302, the door 304 is closed and latched for various reasons.First, the cartridge receptacle 302 and the oxygenation device 54 aresized and shaped in a complementary fashion so that the varioussurfaces, vents, valves, etc. are positioned in a desired manner. Whenthe door 304 is closed and latched, an inner surface 306 of the door 304advantageously presses against a surface 308 of the oxygenation device54 to ensure that the positioning of the oxygenation device 54 isaccurate. Second, the door 304 is advantageously locked to preventremoval of the oxygenation device 54 during normal operation of thesystem 10. Accordingly, the door 304 is provided with a latch 310.Referring to FIGS. 19-26, the door latch 310 includes a handle portion312 and a latching portion 314.

[0131] To latch the door 304, a user grasps the handle portion 312 topivot the latch 310 about a pivot pin 316 generally in the direction ofthe arrow 318. As the latch 310 pivots in the direction of the arrow318, the latching portion 314 hooks around a latch pin 320. The latchpin 320 is coupled to a biasing mechanism 322. The biasing mechanism322, in this embodiment, includes two pins 324 and 326 that extendthrough holes in a wall 328. A respective spring 330 and 332 is disposedabout each pin 324 and 326 to bias the latch pin 320 toward the wall328. As the latching portion 314 hooks around the latch pin 320, thelatch 310 may tend to overcome the bias of the springs 330 and 332 tomove the latching mechanism 322 slightly in the direction of the arrow334. However, due to the bias of the latching mechanism 322, it tends tohold the latch 310, and thus the door 304, tightly in place.

[0132] To keep the latch 310 in place, and thus lock the door 304, alocking mechanism 340 is provided. In this embodiment, the lockingmechanism includes 340 a slidable pin 342 that is disposed in a portionof the wall 328. As the latch 310 moves in the direction of the arrow318, it eventually contacts the front end of the pin 342, and thus movesit in the direction of the arrow 344. The rear portion of the pin 342 iscoupled to a piston 346 of a pull-type solenoid 348. The piston 346 isbiased outwardly by a spring 350, so that the piston 346 is normally inan extended position.

[0133] The latch 310 is configured so that as it reaches its latchedposition, the spring 350 pushes the pin 342 in the direction of thearrow 352 so that the pin 342 extends over a portion 354 of the latch310. With the pin 342 in its locked position over the portion 354 of thelatch 310, the latching portion 314 cannot be removed from the latchingmechanism 322. Instead, the latch 310 remains locked until the piston346 of the solenoid 348 is retracted to move the pin 342 out of the wayof the latch 310.

[0134] It should also be noted that the latch 310 includes a sensor 360that provides an electrical signal indicative of whether the latch 310is in its locked position. In this embodiment, the sensor 360 is a Halleffect sensor. The latch 310 includes a magnet 362 that is positioned toalign with the sensor 360 when the latch 310 is in the locked position.When the magnet 362 is aligned with the sensor 360, the electromagneticsignal is uninterrupted. However, until the magnet 362 reachesalignment, the electromagnetic signal from the sensor 360 isinterrupted, thus indicating that the latch 310 is not yet in its lockedposition.

[0135] Valve Actuation

[0136] As mentioned previously, in the present embodiment, the size andshape of the oxygenation device 54, the contour of the cartridgereceptacle 302, and the closing of the door 304 ensure that theoxygenation device 54 is positioned in a desired manner within thecartridge enclosure 26. Correct positioning is of concern due to theplacement of the valves and vents of the oxygenation device 54 and themanner in which they are controlled and actuated. As mentioned earlier,the valves and vents of the oxygenation device 54 are actuated usingpins in this embodiment. The top of the oxygenation device includesvents 258 and 260, and the bottom of the oxygenation device 54 includesthree valves, 202, 204, and 206. In this embodiment, these vents 258 and260 and valves 202, 204 and 206 are electromechanically actuated usingsolenoid-actuated pins.

[0137] A detailed view of these actuation devices is illustrated inFIGS. 27-32. Referring first to FIG. 27, a bottom view of the cartridgeenclosure 26 is illustrated. The oxygenation device 54 is illustrated byphantom lines. It should be noted that the bottom portion of thecartridge enclosure 26 advantageously includes a slot 380 through whichthe blood return tube 50 of the oxygenation device 54 may pass. Once theoxygenation device 54 is in place within the cartridge enclosure 26, thefill valve 202, the flush valve 204, and the flow valve 206 should be inalignment with respective actuation pins 382, 384, and 386.Advantageously, each of the pins 382, 384, and 386 is tapered at the endto provide an increased tolerance for misalignment. Each of theactuation pins 382, 384, and 386 is moved between a closed position andan open position by a respective solenoid 388, 390, and 392. Each of thesolenoids 388, 390, and 392 is coupled to its respective actuation pin382, 384, and 386 via a respective lever 394, 396, and 398. Each of therespective levers 394, 396, and 398 pivots on a respective fulcrum orpivot pin 400, 402, and 404.

[0138] The manner in which the actuators operate may be understood withreference to FIGS. 28 and 29. While these figures only illustrate theactuator for the flush valve 204, it should be understood that the otheractuators operate the fill valve 202 and the flow valve 206 in the samemanner. As mentioned previously, the valves 202, 204, and 206 arenormally held in a closed position. Accordingly, in this particularembodiment, the solenoids 388, 390, and 392 are pull-type solenoids. Asillustrated in FIG. 28, a piston 406 of the pull-type solenoid 390 isurged into an extended position by a spring 408 that biases one end ofthe lever 396 generally in the direction of the arrow 410. As a result,the spring 408 also biases the actuation pin 384 generally in thedirection of the arrow 412 to maintain the flush valve 204 in its closedposition.

[0139] To allow the flush valve 204 to open, the solenoid 390 isactuated as illustrated in FIG. 29. The actuation of the pull-typesolenoid 390 moves the piston 406 generally in the direction of thearrow 414 into a retracted position. The force of the solenoid 390overcomes the bias of the spring 408 and moves the actuation pin 384generally in the direction of the arrow 416. With the actuation pin 384in a retracted position, the flush valve 204 may open by moving in thedirection of the arrow 416.

[0140] The actuation of the vent valves 258 and 260 takes place in asimilar fashion. Referring now to FIG. 30, a top view of the cartridgeenclosure 26 is illustrated. The top portion of the cartridge enclosure26 also includes a slot 420 through which the IV tube 140 may pass. Oncethe oxygenation device 54 is properly positioned within the cartridgeenclosure 26, the vent valves 258 and 260 align with actuation pins 422and 424, respectively. The pins 422 and 424 are also advantageouslytapered at the ends to increase tolerance to misalignment. Each of theactuation pins 422 and 424 is actuated by a respective solenoid 426 and428. Each of the solenoids 426 and 428 is coupled to the respectiveactuation pin 422 and 424 by a respective lever 430 and 432. Each of thelevers 430 and 432 pivots about a fulcrum or pivot pin 434 and 436,respectively.

[0141] As described with reference to FIGS. 31 and 32, the operation ofthe actuators for the valves 258 and 260 is similar to the operation ofthe actuators for the valves 202, 204, and 206. Although FIGS. 31 and 32illustrate only the actuator for the vent valve 260, it should beunderstood that the actuator for the vent valve 258 operates in asimilar manner. Referring first to FIG. 31, the solenoid 428 in thisembodiment is a pull-type solenoid. A spring 440 generally biases thelever arm 432 in the direction of the arrow 442 to move a piston 444 ofthe solenoid 428 into an extended position. Accordingly, by virtue ofthe action of the lever 432 about the pivot pin 436, the spring 440moves the actuation pin 424 into an extended position. In the extendedposition, the actuation pin 424 exerts pressure on the vent valve 260(not shown) to maintain the vent valve 260 in a closed position.

[0142] To open the vent valves 258 and 260, the solenoids 426 and 428are actuated. As illustrated in FIG. 32, when the pull-type solenoid 428is actuated, the piston 444 moves into a retracted position generally inthe direction of the arrow 446. The force of the solenoid 428 overcomesthe biasing force of the spring 440 and, thus, the lever 432 moves theactuation pin 424 generally in the direction of the arrow 448 into aretracted position. When the actuation pin 424 is in the retractedposition, the vent valve 260 may move upwardly to open and vent gaswithin the mixing chamber 64.

[0143] Cartridge Sensors

[0144] Referring again to FIG. 18, a study of the cartridge receptacle302 reveals that a number of sensors are utilized to monitor and/orcontrol the system 10 in general and the oxygenation device 54 inparticular. Due to the nature of the information to be gathered and thetypes of sensors used to gather this information, the oxygenation device54 and the sensors include certain features that facilitate thegathering of such information in a more accurate and robust manner.However, it should be appreciated that other types of sensors and/orfeatures may be utilized to gather similarly relevant information foruse in monitoring and/or controlling the system 10 and oxygenationdevice 54.

[0145] As will be appreciated from a detailed discussion of theelectronic controls of the system 10, it is desirable to monitor andcontrol fluid levels within the atomization chamber 62 and the mixingchamber 64. Accordingly, an AO level sensor 480 is provided to monitorthe level of aqueous oxygen within the atomizer chamber 62, and a highlevel sensor 482 and a low level sensor 484 are provided to monitor thelevel of the oxygen-enriched blood within the mixing chamber 64. Asmentioned above, because the oxygenation device 54 is configured as areplaceable cartridge in this exemplary embodiment, the sensors havebeen placed within the cartridge enclosure 26 instead of within theoxygenation device 54. Thus, the level sensors 480, 482, and 484 do notactually contact the fluid within the chambers 62 and 64. Were thesensors 480, 482, and 484 to contact the liquid, they could becomecontaminated and, thus, the sensors would typically be replaced eachtime the system 10 was used for a different patient. Since this wouldlikely add to the cost of replacement items, and potentially affect thesterility of the system, from both a user's standpoint and a patient'sstandpoint, it is desirable that the sensors do not contact the liquidwithin the oxygenation device 54.

[0146] In this embodiment, the sensors 480, 482, and 484 are ultrasonicsensors. Because ultrasonic waves travel more efficiently through solidsand liquids than through air, it is desirable that the sensors 480, 482,and 484 and/or the oxygenation device 54 be configured in a manner whichpromotes the efficient transmission and reception of ultrasonic waves.In this embodiment, both the sensors 480, 482, and 484 and theoxygenation device 54 include features which prove advantageous in thisregard.

[0147]FIGS. 19 and 33 are cross-sectional views of the cartridgeenclosure 26 that illustrate the high level sensor 482 and the AO levelsensor 480, respectively. Although the low level sensor 484 is notillustrated in cross-section, it should be understood that itsconstruction is similar to or identical to the construction of thesensors 480 and 482. Furthermore, detailed views of the sensors 482 and480 are illustrated in FIGS. 34 and 35, respectively, again with theunderstanding that the sensors 480, 482, and 484 are substantiallyidentical in regard to the details shown in these Figs.

[0148] To ensure that physical contact is maintained between theoxygenation device 54 and the sensors 480, 482, and 484, the sensors areadvantageously biased into contact with the oxygenation device 54. Thesensors 480, 482, and 484 actually utilize a spring-biasing technique,although various other types of biasing techniques may be utilized toachieve similar results. In this example, an ultrasonic transducerelement 490 is disposed within a channel 492 formed within a sensor body494. The sensor body 494 may be formed in any suitable shape, but it isillustrated in this embodiment as being cylindrical. The sensor body 494is slidably disposed within a sleeve 496. The sleeve 496 is fixedlydisposed in a wall 498 of the cartridge enclosure 26. For example, thesleeve 496 may have external screw threads 500 so that the sleeve 496may be screwed into a threaded bore in the wall 498. To facilitateslidable movement of the sensor body 494 within the sleeve 496, abushing 502 may be provided within the sleeve 496. In this example, thesensor body 494 includes an annular flange 504 that abuts against oneend of the bushing 502 in order to limit outward movement of the sensorbody 494. A spring 506 is disposed in the rear portion of the sleeve496. The spring 506 abuts against the opposite side of the annularflange 504 to bias the sensor body 494 generally in the direction of thearrow 508. The bushing 502 may be adhered to, or an integral part of,the sleeve 496, or it may be held in place by an external seal or cap510.

[0149] Although the spring-loaded construction of the sensors 480, 482,and 484 tends to bias the sensors into contact with the oxygenationdevice 54 to facilitate the efficient transmission of ultrasonic energy,the nature of the contact between the end of the sensor and theoxygenation device 54 is also important for efficient ultrasonic wavetransmission. Hence, to improve this contact region, the sensors 480,482, and 484 include a resilient member 512, such as a rubber cap. Theresilient member 512 is able to deform slightly as it contacts theoxygenation device 54 to ensure that a good contact is made. To enhancethe contact region further, the oxygenation device 54 advantageouslyincludes flat contact portions 514 and 516, respectively, so that thecontour of the oxygenation device 54 matches the contour of theresilient member 512. In addition, to enhance the ultrasonic contacteven further, a suitable gel may be used between the oxygenation device54 and the sensors 480, 482, and 484.

[0150] The cartridge enclosure 26 advantageously includes other sensorsas well. For example, it may be desirable for the system 10 to be ableto determine whether the oxygenation device 54 has been inserted withinthe cartridge enclosure 26. To provide this information, a cartridgepresent sensor 520 may be disposed within the cartridge enclosure 26. Inthis example, the cartridge present sensor 520, as illustrated in FIG.19, may be a reflective infrared sensor that is positioned within anopening 522 in the wall 498 of the cartridge enclosure 26. Unlike theultrasonic sensors discussed previously, the efficiency of a reflectiveinfrared sensor is not improved by physical contact. Indeed, theefficiency of a reflective infrared sensor relates more to the nature ofthe surface reflecting the infrared energy back to the sensor. In otherwords, if the surface is irregular, the infrared energy transmitted fromthe infrared sensor may scatter so that little or no infrared energy isreflected back to the sensor. On the other hand, if the surface issmooth, generally perpendicular to the sensor, and/or reflective, ittends to maximize the amount of infrared energy reflected back to thesensor. Accordingly, the portion of the oxygenation device 54 positionedadjacent the cartridge present sensor 520 is advantageously configuredto promote reflection of infrared energy back to the cartridge presentsensor 520. In this example, the oxygenation device 54 advantageouslyincludes a flat section 524 to ensure that the cartridge present sensor520 receives a relatively strong reflective signal so that it canproperly indicate whether the oxygenation device 54 is present.

[0151] It may also be desirable to monitor the temperature of theaqueous oxygen formed within the atomizer chamber 62. The temperature ofthe aqueous oxygen is a useful parameter because the oxygenation levelof the aqueous oxygen, and ultimately the oxygenation level of theoxygen-enriched blood, may vary with temperature. If it is desirable totake a temperature measurement into account to monitor and control thefunctioning of the oxygenation device 54 and the system 10, thetemperature may be sensed in a variety of different areas. For example,a simple room temperature sensor may be incorporated somewhere withinthe system 10, using the assumption that the physiologic solution to beoxygenated will typically be at room temperature. Alternatively, thetemperature of the oxygenation device 54 may be monitored, using theassumption that the aqueous oxygen within the oxygenation device 54 willbe at the same temperature.

[0152] However, to provide the greatest level of control, it may bedesirable to measure the temperature of the aqueous oxygen within theatomizer chamber 62. Although a thermocouple could be disposed in theatomizer chamber 62 of the oxygenation device 54 with appropriateelectrical contacts extending out of the oxygenation device 54, the useof a sensor within a disposable device would only increase the cost ofthe device. Accordingly, it may be desirable to utilize a sensor that isexternal to the atomizer chamber 62 and yet still able to monitor thetemperature of the aqueous oxygen within the atomizer chamber 62. Toachieve this function in this example, an external temperature sensor540 is coupled within an opening 542 in the wall 498 of the cartridgeenclosure 26 as illustrated in FIG. 33. The temperature sensor 540 maybe, for example, a pyroelectric sensor or a piezoelectric sensor.Changes in the temperature of the AO solution within the atomizerchamber 62 will alter the frequencies of such signals and, thus,indicate the actual temperature of the AO solution.

[0153] Gas Coupling

[0154] The cartridge enclosure 26 also includes another interestingfeature regarding the manner in which it interfaces with the oxygenationdevice 54. As previously discussed, the oxygenation device 54 includesan oxygen inlet 210 located near the top of the atomizer chamber 62. Asalso previously mentioned, a supply of oxygen 60 regulated to about 600psi is coupled to the oxygen inlet 210. Thus, it may be desirable toprovide a connection to the inlet 210 that effectively handles suchpressure and does not require user intervention.

[0155] Referring to FIG. 36, the oxygen supply 60 is typically enabledby a flow valve 600. The flow valve 600 delivers oxygen through apressure transducer 602 and a check valve 604. The oxygen then proceedsthrough a tee 606 and into a line 608. The line 608 is coupled to aplunger 610 illustrated in the cross-sectional view of FIG. 37. Theplunger 610 includes a port 612 that runs laterally from the line 608and then downwardly into the cartridge cavity 302. The plunger 610 isslidably disposed within a bushing or sleeve 614. As best illustrated inthe detailed views of FIGS. 38 and 39, the sleeve 614 includes arecessed area 616 in which a spring 618 is disposed. The spring tends tobias the plunger 610 upwardly so that the coupling portion 620 of theplunger 610 that is configured to seal against the oxygen inlet 210 ofthe oxygenation device 54 is recessed slightly.

[0156] The top of the plunger 610 includes a slanted or cammed portion622 that abuts in a complimentary relationship with a slanted or cammedportion 624 of a rod 626. The rod 626 is slidably disposed within anopening 628 in the cartridge enclosure 26. The rod 626 is biased in thedirection of the arrow 630 in an extended position by a spring 632. Asbest illustrated in FIG. 39, when a user closes the door 304, the rod626 is moved in the direction of the arrow 634 against the bias of thespring 632. As the rod 626 moves back against the spring 632, the cammedsurfaces 622 and 624 slide against one another, thus forcing the plunger610 downwardly in the direction of the arrow 636 to seal the couplingportion 620 against the oxygen inlet 210. The rod 624 is advantageouslyprovided with an adjustment screw 638. The adjustment screw 638 may beadjusted so that the abutment portion 640 of the rod 626 is in anappropriate position to ensure that the coupling portion 620 of theplunger 610 solidly seals against the oxygen inlet 210 when the door 304is closed and latched.

[0157] Piston Drive Mechanism

[0158] To this point in the discussion, all of the various interfacesbetween the cartridge receptacle 302 and the oxygenation device 54 havebeen discussed with the exception of one. As mentioned previously, theoxygenation device 54 includes a piston assembly 160 that is configuredto draw physiologic solution into the chamber 58 and to deliver it underpressure to the atomization chamber 62. As illustrated in FIG. 8, theplunger 164 includes a key 176 at one end. As mentioned during thatdiscussion, the key 176 is configured to fit within a key slot of adevice that moves the piston assembly 160 between its extended andretracted positions.

[0159] Although a variety of different mechanisms may be used to achievethis function, the drive mechanism utilized in the present embodiment isillustrated in FIG. 40 and generally designated by the reference numeral700. Generally speaking, the drive mechanism 700 includes a ball screwmechanism 702 that is driven and controlled by a motor 704. In thisembodiment, the motor 704 is a stepper motor whose position is monitoredby an optical encoder 706. Although the motor 704 may be directlycoupled to the ball screw mechanism 702, a transmission 708 is used totransfer power from the motor 704 to the ball screw mechanism 702 inthis embodiment. Specifically, an output shaft 710 of the motor 704 iscoupled to a gear 712. The gear 712 meshes with a gear 714 that isoperatively coupled to turn a screw 716. In this embodiment, the gears712 and 714 have a drive ratio of one to one. However, any suitabledrive ratio may be used.

[0160] As the motor 704 turns the screw 716, a “drive” assembly 718rides up or down the screw 716 generally in the direction of the arrow720 depending upon the direction of rotation of the screw 716. A ram 722is slidably disposed about the screw 716 at the top of the driveassembly 718. The ram 722 includes a key way 724 that is configured toaccept the key 176 of the piston assembly 160. Hence, as the ram 722moves up and down with the drive assembly 718 in response to rotation ofthe screw 716, it moves the piston assembly 160 back and forth withinthe chamber 58.

[0161] The drive assembly 718 advantageously includes a load cell 726that is loaded as the ram 722 extends to drive the piston assembly 160into the chamber 58. The force exerted on the load cell 726 relates tothe fluid pressure within the chamber 58 when the piston assembly 160 isdriving fluid out of the passageway 190. Accordingly, the reading fromthe load cell 726 may be used to control the speed and position of theram 722 to ensure that fluid is delivered to the atomization chamber 62at the desired pressure.

[0162] The components of the stepper motor assembly 700 are more clearlyillustrated in the exploded view of FIGS. 41A and 41B. In addition tothe components previously discussed, it can be seen that the gears 712and 714 ride on respective bearings 730 and 732. The motor 704 ismounted to one side of a bracket 734, while a shroud 736 that surroundsthe drive assembly 718 is mounted on the other side of the bracket 734.It can further be seen that the screw 716 is mounted within a coupling738 that rides on a tapered thrust bearing 740. The thrust bearing 740is useful for accommodating the force of thrusting the ram 722 upwardlyto drive the piston assembly 160 into the chamber 58.

[0163] The drive assembly 718 includes a nut 742 that is threadablycoupled to a load cell mount 744. Referring additionally to thecross-sectional view of FIGS. 42 and 43, the load cell mount 744includes a slot 746 having a closed end. When the load cell mount 744 isplaced within the shroud 736, the slot 746 is aligned with a set pin748. The set pin 748 is disposed within the slot 746 to prevent thedrive assembly 718 from bottoming out as it moves downwardly in responseto rotation of the screw 716. Instead, the drive assembly 718 stops whenthe end of the slot 746 meets the set pin 748.

[0164] It should also be appreciated that the drive assembly 718 shouldmove axially, not rotationally, in response to rotation of the screw716. To accomplish such movement, a guide 737 is disposed on the innerwall of the shroud 736. The guide 737 interfaces with a slot 747 in theload cell mount 744 to prevent rotation of the drive assembly 718 as itmoves up and down along the screw 716. Rather, because the driveassembly 718 is prevented from rotating, it moves axially relative tothe screw 716.

[0165] The lower end of the ram 722 includes a flange 750. The flange750 impinges upon the top portion of a load cell cover 752, and a lockring 754 is coupled to the bottom of the ram 722 to fix the load cell726 and the load cell cover 752 onto the ram 722. The load cell cover752 is further coupled to the load cell mount 744 by a screw 756.Finally, the upper end of the ram 722 is placed through a bearing 758,and a cover plate 760 is screwed onto the top of the shroud 736.

[0166] The stepper motor assembly 700 further includes a sensor assembly800 as illustrated in FIGS. 44-48. The sensor assembly 800 provides twosignals to the system controller 55. The first signal is generated whenthe drive assembly 718, and thus the piston assembly 160, has reachedits maximum travel, i.e., its maximum extension. The second signal isprovided when the drive assembly 718, and thus the piston assembly 160,reaches its home position, i.e., maximum retraction. The maximum travelsignal is useful to ensure that the cap 166 of the piston assembly 160does not bottom against the end of the chamber 58. The home positionsignal is useful for resetting the optical encoder 706 so that it canstart monitoring the motor 704 from a known position of the driveassembly 718.

[0167] As illustrated in FIGS. 44 and 46, the sensor assembly 800includes a maximum travel sensor 802 and a home position sensor 804. Inthis embodiment, the sensors 802 and 804 are optical sensors. Thus, asbest illustrated in FIG. 48, each of the sensors 802 and 804 includes anoptical transmitter 806 and an optical receiver 808. So long as the pathbetween the optical transmitter 806 and optical receiver 808 remainsclear, the optical receiver 808 receives the optical signal transmittedfrom the optical transmitter 806. However, if an obstruction comesbetween the optical transmitter 806 and the optical receiver 808, theoptical receiver 808 does not receive the optical signal sent from theoptical transmitter 806. Thus, the output of the optical sensor 802 or804 will change in this circumstance to indicate that an obstruction ispresent.

[0168] In the present embodiment of the sensor assembly 800, a tab orflag 810 is coupled to the load cell mount 744, as best illustrated inFIG. 47. In this embodiment, screws 812 and 814 are used to couple theflag 810 to the load cell mount 744, although any suitable mountingarrangement may be utilized. FIGS. 46 and 47 illustrate the driveassembly 718 in the home position. Accordingly, the flag 810 ispositioned between the optical transmitter 806 and the optical receiver808 of the home position sensor 804.

[0169] General System Operation

[0170] Now that the various mechanical components of the system 10 havebeen discussed, the manner in which the system 10 operates under thecontrol of various electrical components may now be discussed. Turningnow to FIG. 49, a state diagram 900 depicts the basic operation of thisembodiment of the system 10.

[0171] When the system 10 is powered on or reset, it enters aninitialization mode 902. In the initialization mode, the systemcontroller 55 sets various system parameters and performs variousdiagnostic checks. For example, if the system 10 was powered downimproperly the last time it was turned off, an error code may beprovided. Furthermore, if the system 10 experiences a watchdog timerfailure, which typically means that its processor is lost or notfunctioning properly, the system will enter a watchdog failure mode 904.

[0172] In the initialization mode 902, the system controller 55 alsoreads the cartridge present signal delivered by the sensor 520. Asillustrated in FIG. 50, the cartridge present signal is processed by anIO register subsystem 906 prior to processing by the CPU 908. If anoxygenation device 54 is present within the cartridge enclosure 26, thesystem switches from the initialization mode 902 into an unload mode910. In the unload mode 910, the oxygenation device 54 is depressurizedand the door is unlocked to allow removal of the oxygenation device 54.Removal of a used oxygenation device 54 is desirable to ensure that thesame oxygenation device 54 is not used for multiple patients. Todepressurize the oxygenation device 54, the system controller 55delivers an O₂ vent signal 912 to the solenoid 426 associated with theatomizer chamber 62 and a blood mixing chamber vent signal 914 to thesolenoid 428 associated with the mixing chamber 64. As discussedpreviously, the solenoids 426 and 428 respond by retracting therespective pins 422 and 424 to enable the vent valves 258 and 260 toopen. Once the oxygenation device 54 has been depressurized, the systemcontroller 55 disables a door lock signal 916 which causes the solenoid348 to retract and withdraw the locking pin 342 from the door latch 310.

[0173] If the user does not unload the oxygenation device 54 within 30seconds, a timeout occurs and the system 10 switches into a wait state920, labeled wait mode 3. In the wait mode 3 state 920, an unloadcommand will continue to be delivered so that the system 10 switchesbetween the unload mode 910 and the wait mode 3 state 920 until the userhas completed the unload operation. Then, when the oxygenation device 54is not present, the system switches from the wait mode 3 state 920 backinto the initialization mode 902.

[0174] Once initialization is complete, the system 10 switches into await mode 1 state 922. In the wait mode 1 state 922, the systemcontroller 55 monitors a RS232 serial communications port 924 to await aload command from the host/user interface 66. Upon receipt of the loadcommand, the system 10 switches into a load mode 926. The load mode 926allows a user to install a new oxygenation device 54 and to prepare thesystem for priming. In the load mode 926, all valve actuation pins 382,384, 386, 422, and 424, as well as the door lock pin 342, are retracted.Retraction of the valve actuation pins is desirable because the extendedactuation pins may inhibit the oxygenation device from being installedproperly within the cartridge enclosure 26. To retract the respectivevalve actuation pins 382, 384, 386, 422, and 424, as well as the doorlock pin 342, the system controller 55 delivers a fill signal 930, aflush signal 932, an AO flow signal 934, an O₂ vent signal 912, a bloodmixing chamber vent signal 914, and a lock signal 916, to the solenoids388, 390, 392, 426, 428, and 348, respectively.

[0175] Like the unload mode 910 described previously, the load mode 926also includes a timer, such as a 30 second timeout, which causes thesystem 10 to revert from the load mode 926 back to the wait mode 1 state922 if the user has not loaded the oxygenation device 54 in the allottedtime. However, once the user has successfully loaded the oxygenationdevice 54 within the cartridge enclosure 26 as indicated by thecartridge present signal 520, the valve actuation pins 382, 384, 386,422, and 424, as well as the door lock pin 342, are all extended so thatthe respective valves 202, 204, 206, 258, and 260 are held in theirclosed positions, and so that the latch 310 will lock when the door 304is closed.

[0176] Once the door 304 has been closed and locked, the load operationis complete, and the system 10 switches from the load mode 926 into await mode 2 state 940. In the wait mode 2 state 940, the systemcontroller 55 monitors the RS232 serial communications port 924 to awaiteither a prime command or an unload command. If the unload command isreceived, the system 10 transitions into the unload mode 910, whichoperates as previously discussed. However, if the prime command isreceived, the system 10 transitions into a prime mode 942.

[0177] A user initiates the prime mode 942 by pressing the prime switch108. In the prime mode 942, the system 10 fills the fluid supply chamber58 with physiologic solution and drives the piston assembly 160 topressurize the solution and transfer it into the atomizer chamber 62until the appropriate level of fluid is reached. In the prime mode 942,a stepper motor drive subsystem 950 of the system controller 55 readsthe position of the stepper motor 704 from the encoder 706 and drivesthe stepper motor 704 to cause the ram 722 to push the piston assembly160 into its fully extended position within the fluid supply chamber 58.As the piston assembly 160 is retracted, physiologic solution is drawninto the fluid supply chamber 58 through the passageway 144. The pistonassembly 160 then extends again to pressurize the physiologic solutionwithin the fluid supply chamber 58 and to transfer it from the fluidsupply chamber 58 into the atomizer chamber 62. In this mode, the fillvalve 202 is opened, so that the fluid enters the atomizer chamber 62through the tube 232 rather than through the atomizer 216.

[0178] When the system controller 55 receives the signal from the AOlevel sensor 480 indicating that the atomizer chamber 62 has beenappropriately filled, the stepper motor driver subsystem 950 retractsthe piston assembly 160 to the home position and then extends the pistonassembly 160 to transfer an additional amount of solution, e.g., 3 ccs,into the atomizer chamber 62. After the atomizer chamber 62 has beenprimed with the physiologic solution, the system controller 55 deliversan O₂ flow signal 952 to an O₂ flow solenoid 954 to open a valve 956 andallow the oxygen from the supply 60 to pressurize the atomizer chamber62.

[0179] Once the proper level of fluid has been reached, the prime mode942 is complete. However, prior to completion of the priming operation,the system 10 may transfer from the prime mode 942 to the wait mode 2state 940 if the priming operation is interrupted by a halt commandtransmitted as either a result of an error in the priming operation oras a result of the user pressing the stop switch 112.

[0180] Once the prime mode 942 is complete, the system 10 transitionsinto an AO off mode 960. While in the AO off mode 960, no aqueous oxygenis produced or delivered. Instead, the system controller 55 delivers aflush signal 932 to the solenoid 390 to open the flush valve 204. Aspreviously discussed, when the flush valve 204 is open, physiologicsolution flows from the fluid supply chamber 58 through the valveassembly 200 and into the mixing chamber 64 through the capillary tube246. This mode of delivery continues so long as the blood flow throughthe mixing chamber 64 is above a predetermined rate, e.g., 50 ml perminute. If the blood flow drops below the predetermined rate, the system10 transitions into a timeout mode 962. In the timeout mode 962, thesystem 10 does not flow, fill, or flush, and the piston assembly 160returns to the home position. The system 10 will transition from thetimeout mode 962 to the unload mode 910 if either the unload command isreceived from the host/user interface or if the system 10 has been inthe timeout mode 962 for a predetermined time, e.g., 150 seconds.However, once blood flow rises above the predetermined rate, the systemtransitions from the timeout mode 962 back to the AO off mode 960.

[0181] When the AO on command is received, the system 10 transitionsfrom the AO off mode 960 to an AO on mode 964. The AO on command isproduced when the user presses the prime button 108 and the start button110 simultaneously. In the AO on mode 964, the priming signal isdelivered from the blood pump system 24 on a line 966 to the interlocksystem 44. If the system controller 55 is in the AO off mode 960 whenthe prime command is received, then the logic block 134 of the interlocksystem 44 delivers an enable signal on line 126 to enable the blood pump24. The logic block 134 also delivers a draw clamp signal on a line 970to the draw clamp 78 to open it while the return clamp 80 remainsclosed. The logic block 130 also delivers a prime signal on a line 968to the CPU 908 of the system controller 55. In response to receiving theprime signal, the system controller 55 monitors the low level sensor 484to determine when enough blood has flowed into the mixing chamber 64 forthe chamber to be filled to the level indicated by the low level sensor484. The low level signal is also sent to the logic block 134 of theinterlock system 44 via a line 974. When the interlock system 44determines that the chamber 64 has been filled to the level indicated bythe low level sensor 484, it delivers a return clamp signal on a line972 to the return clamp 80 to open it. Simultaneously, the systemcontroller 55 delivers a cyclox vent signal 914 to the solenoid 428 inorder to close the vent valve 260.

[0182] The system 10 continues to operate in the AO on mode 964 in thismanner unless blood flow drops below a predetermined rate, e.g., 50 ml.per minute. In this instance, the system 10 will transfer from the AO onmode 964 to the unload mode 910, which will operate as discussedpreviously.

[0183] The logic block 134 of the interlock system 44 also delivers anAO enable signal on a line 976 to the CPU 908 of the system controller55. The AO enable signal causes the system controller 55 to deliver anAO flow signal 934 to the solenoid 392 to open the flow valve 206. Asdiscussed previously, with the flow valve 206 opened, aqueous oxygenflows from the atomizer chamber 62 through the capillary tube 246 andinto the mixing chamber 64 to be mixed with the blood.

[0184] Bubble Detector

[0185] As mentioned previously, the system 10 advantageously includes abubble detector 74 that interfaces with a bubble sensor 76 to monitorthe oxygen-enriched blood in the return tube 50 for bubbles. Anexemplary embodiment of the bubble detector 74 is illustrated in FIG.51. The bubble detector 74 includes a digital signal processor (DSP)1000 that operates under software control to perform many of thefunctions of the bubble detector 74. The bubble detector 74 receives areturn pressure signal and a flow rate signal from the interlock system44 on lines 1002 and 1004, respectively. An analog-to-digital converter(ADC) 1006 receives these analog signals and converts them to digitalsignals. These digital signals are transmitted from the ADC 1006 to amicrocontroller 1008. The microcontroller 1008 also receives user inputfrom an RS-232 serial communications port 1010 from the host/userinterface 66, as well as an initiate signal on line 1012 from theinterlock system 44.

[0186] The DSP 1000 and the microcontroller 1008 interface with oneanother via interface and control logic 1014. Based on inputs from theDSP 1000 and the microcontroller 1008, the interface and control logic1014 delivers a transducer driver signal on line 1016 to a transducerdriver 1018. In response, the transducer driver 1018 delivers a signalto the transducer 76 via line 1020. As illustrated in FIG. 52, thetransmitted signal delivered by the transducer 76 includes bursts ofhigh frequency pulses 1023A and 1023B. Each pulse burst may include 20pulses for instance at 3.6 MHz, with microseconds between bursts. Areturn signal from the transducer 76 is received on the line 1022. Thesignal received from the transducer 76 on line 1022 resembles thetransmitted signal 1021, but it is shifted later in time and has asmaller amplitude. It typically takes longer than one burst period for abubble to pass by the transducer 76. Therefore, each bubble may besampled each time a pulse is delivered during the burst period, e.g., inthis example, each bubble may be sampled 20 times as it travels past thetransducer 76.

[0187] The strength of the received signal on the line 1022 relative tothe transmitted signal on the line 1020 provides information regardingthe presence of bubbles within the return tube 50. As illustrated inFIG. 54, the bubble sensor 76 includes an ultrasonic transmitter 1040and an ultrasonic receiver 1042. The bubble sensor 76 is advantageouslydisposed on the outside of the return tube 50. Thus, the ultrasonicsignal from the transmitter 1040 is transmitted through the return tube50, as well as any fluid within the return tube 50, to the receiver1042. If the fluid in the return tube 50 contains no bubbles, theultrasonic signal propagates from the transmitter 1040 to the receiver1042 in a relatively efficient manner. Thus, the signal strength of thereturn signal delivered by the receiver 1042 on the line 1022 isrelatively strong. However, if the fluid within the return tube 50contains bubbles 1044, as illustrated in FIG. 55, the ultrasonic signalreceived by the receiver 1042 will be weaker. The poorer transmission ofthe ultrasonic signal across fluid containing bubbles results from thefact that the bubbles 1044 tend to scatter the ultrasonic signal so thatless of the transmitted signal is ultimately received by the receiver1042.

[0188] As illustrated by way of example in FIG. 53, the first peak 1027Adepicts a signal that was transmitted through fluid containing nobubbles, and the second peak 1027B depicts a signal that was transmittedthrough fluid containing bubbles. The relative weakness of the peak1027B is demonstrated by a reduction in the peak 1027B. The extent ofthe reduction in the peak 1027B is related to the diameter of the bubblepassing through the bubble sensor 76 at the time the signal wastransmitted. Specifically, the amount of the reduction 1046 in thesignal is related to the square of the diameter of the bubble, so thatthe square root of the signal is directly proportional to the size ofthe bubble.

[0189] To facilitate processing of the return signal, it is delivered toa signal conditioner 1024. The signal conditioner 1024 amplifies andfilters the return signal. The signal conditioner 1024 then detects theamount of ultrasonic energy of the signal and transmits it to an analogto digital converter (ADC) 1026. A signal 1025 delivered to the ADC 1026is illustrated in FIG. 53. As can be seen from a study of the signal1025, each of the high frequency pulse trains 1023A and 1023B nowresembles a single peak 1027A and 1027B, respectively. The ADC 1026samples only the peaks 1027A and 1027B in the amplitude signal 1025. Inthis example, each peak 1027A and 1027B is approximately 6.6microseconds in width, and the ADC 1026 samples 128 peaks to establish128 data points.

[0190] The digitized output of the ADC 1026 is delivered to a buffer,such as a firstin/first-out (FIFO) buffer 1030. The buffer 1030 storesthe digitized representations of 128 peaks and delivers them one by oneto the DSP 1000. The interface and control logic 1014 controls deliveryof the signals from the buffer 1030 to the DSP 1000.

[0191] The DSP 1000 reads the data points for each of the digitizedpeaks and sums them together. The sum of the digitized peaks correlatesto the amount of ultrasonic energy received. In this embodiment, the DSP1000 maintains a running average of the sum of the last 16,000 or morepeaks. The current sum is subtracted from the average to provide a highpass filter which effectively removes any DC offset. The DSP 1000 alsoperforms a low pass filter operation by convolving the resulting signalthrough an FIR array. In this example, the FIR array is a 64 pointarray. The filtering is performed to ensure that the bubbles arediscriminated from the noise in the signals. The resulting signals ofdifferent sized bubbles is illustrated in FIG. 61.

[0192] Once the DSP 1000 determines the diameter of each bubbledetected, it calculates the volume of the bubble. However, it should beunderstood that the volume of the bubble delivered to the patient 38 isaffected by the pressure of the fluid within the return tube 50. Becausethe pressure of the fluid within the return tube 50 is typically higher,e.g., approximately two to three atmospheres, as compared to the bloodwithin the patient's vessels, e.g., approximately one atmosphere, aconversion is advantageously performed to determine the volume of thebubble once it reaches the patient 38. Since the pressure in the returntube 50 is delivered to the bubble detector 74 on the line 1002, andsince the pressure of the patient's blood can be assumed to be oneatmosphere, the volume of the bubble at the patient equalsV_(p)=(P_(s)·V_(s))/P_(a), where V_(p) is the volume of the bubble atthe patient 38, Ps is the pressure at the bubble sensor 76, Vs is thevolume of the bubble at the bubble sensor 76, and Pa is atmosphericpressure.

[0193] The DSP 1000 advantageously places bubbles of certain sizes inappropriate “bins” or categories. In other words, the DSP 1000 maymaintain different categories of bubble sizes. For example, thecategories may include sixteen bins of 75 micron diameter increments.The number of bubbles in each category may be transmitted to the display32 so that a user can monitor the number and size of bubbles beingproduced during the surgical procedure. The number and size of bubblesalso may be monitored by the bubble detector 74 or elsewhere within thesystem 10 to monitor the operation of the system 10.

[0194] The bubble detector 74 also may add the volume of each bubble toa running total. If the running total exceeds a prescribed volume withina prescribed time, then operation of the system 10 may be altered. Forexample, if the total volume of bubbles exceeds 10 microliters in a 90minute period, the bubble detector 74 may deliver a “request to stop”signal on a line 1050. In this embodiment, the request to stop signal isreceived by the interlock system 44, so that the interlock system 44 canshut down the system 10 as previously described. Since most patientstypically resolve small volumes of gas over time, the running total maybe decremented as the procedure progresses so that the predeterminedlimit which triggers shut down of the system 10 will not be reached asrapidly. In addition, prior to reaching the predetermined limit, thebubble detector 74 may provide an early warning of an impending shutdown so that the system controller 55 can lower the pO₂ level of theblood in the return tube 50 to curtail bubble production and, thus,avoid shutdown.

[0195] Bubble Detector Evaluation or Calibration

[0196] Individual ultrasonic probes may have varying degrees ofresolution. Therefore, a limitation on the bubble detector's ability todetect bubbles may arise when the size and/or velocity of some bubblesare beyond the resolution of the probe. Depending on the circumstances,it is possible that microbubbles (bubbles with diameters of about 50 μmto about 1000 μm) and/or macrobubbles (bubbles with diameters greaterthan 1000 μm) may escape detection. When bubbles escape detection, theaccuracy of the bubble detector may be compromised.

[0197] Thus, it may be desirable to utilize a system and method forevaluating the bubble detection capabilities of a bubble detector. Thesystem and method of evaluation described below is capable ofdetermining the microbubble and macrobubble reolution of the bubbledetector at a plurality of flow rates and material viscosities.Generally speaking, bubbles of a determinable size are introduced into aflow material. The size and quantity of bubbles introduced into the flowmaterial are measured by the bubble detector under evaluation.Thereafter, the size and quantity of bubbles introduced into the flowmaterial are determined independently.

[0198] An exemplary embodiment of a calibration and evaluation system1105 for bubble detectors, such as the bubble detector 74, isillustrated in FIG. 56. The system and method permits a practitioner tocontrol the bubble size, rate of bubble production, and the rate of flowof flow material. The system 1105 employs a containment vessel 1110 forstoring a flow material 1112. The vessel 1110 includes an inlet 1116 andoutlet 1118 so that the flow material 1112 travels generally in thedirection of the arrow 1119. A pump 1120, such as a peristaltic pump, isutilized to induce and maintain a desired flow rate. Advantageously, thepump 1120 is capable of transmitting the flow material 1112 at aplurality of flow rates. Flow materials 1112 of varying viscosity may beutilized and may include newtonian or non-newtonian fluids. Typically,the viscosity of the flow material 1112 used for evaluation iscomparable with the viscosity of the material utilized in theoperational environment, e.g., blood mixed with gas-enriched physiologicfluid in this example.

[0199] The system 1105 employs a first conduit 1130, typically ofpredetermined internal diameter and predetermined length, having aproximal end 1132 and distal end 1134, through which the flow material1112 may be passed at various rates. The proximal end 1132 is coupled tothe outlet 1118 to receive the flow material 1112 from the vessel 1110.The distal end 1134 is coupled to a connecting device 1140. Theconnecting device 1140, for example a T-connector, is typicallypositioned along the longitudinal axis of the first conduit 1130 and influid communication therewith to permit the continued unimpeded flow ofthe flow material 1112.

[0200] A bubble-forming device 1143 may be used to induce bubbleformation in the flow material 1112 through the introduction of abubble-forming material 1150. The bubble-forming material 1150 typicallyincludes a gas, such as air. The flow material 1112 may contain asurfactant, such as sodium dodecyl sulfate (SDS), to promote bubbleformation and retention.

[0201] As best illustrated in FIGS. 57 and 58, the bubble-forming device1143 in this example includes a bubble-forming capillary 1144, which istypically of predetermined internal diameter and predetermined length.The capillary 1144 has a proximal end 1146 and a distal end 1148. Theproximal end 1146 is attached by a bubble-forming lumen 1153 to abubble-pumping device 1155, such as a syringe. The bubble-pumping device155 is typically capable of injecting the bubble-forming material 1150into the flow material 1112 at various injection rates. The distal end1148 of the capillary 1144 is slidably arranged to be located within theinterior of the connecting device 1140 incident to the flow material1112, thus resulting in the generation of bubbles within the flowmaterial 1112. In this example, the capillary 1144 is positionedperpendicular or nearly perpendicular to the longitudinal axis of thedirection of flow of the flow material 1112 so that the resultant shearforce of the flow generates bubbles of a uniform size at a constantrate.

[0202] Bubble size may be regulated by the internal diameter of thecapillary 1144 or by positioning the distal portion 1148 of thecapillary 1144 at various positions within the material flow. Increasingthe internal diameter of capillary 1144 increases bubble size.Similarly, positioning the distal portion 1148 of the capillary 1144away from the longitudinal axis of the flow material 1112 increasesbubble size. The rate of bubble formation may be varied by increasing ordecreasing the flow rate of the bubble-forming material 1150 introducedinto the flow material 1112. For example, an increase in the flow rateof the bubble-forming material 1150 increases the rate of bubbleformation in the flow material 1112.

[0203] The system 1105 further employs a second conduit 1170, which istypically of predetermined internal diameter and predetermined length. Aproximal end 1172 of the second conduit 1170 is coupled to theconnecting device 1140, and a distal end 1174 of the second conduit 1170is coupled to the inlet 1116 of the containment vessel 1110. To maintaina substantially constant flow rate in the conduits 1130 and 1170, thesecond conduit 1170 is usually coaxially aligned with the first conduit1130, and the diameter of the second conduit 1170 is usually equivalentto the diameter of the first conduit 1130. The probe 76 of the bubbledetector 74 to be evaluated is positioned proximal to the second conduit1170 to enable detection of bubbles within the flow material 1112passing through the second conduit 1170.

[0204] The connecting device 1140 may be optically transparent to permitvisual inspection of the bubble generation process. Indeed, a recordingdevice 1160, such as a CCD camera, may be focused on the distal end 1148of the capillary 1144 to observe and record the size and quantity ofbubbles within the flow material 1112. Thus, bubble detectors, such asthe bubble detector 74 for example, may be calibrated by comparing thesize and quantity of bubbles detected by the probe 76 with the size andquantity of the bubbles measured by the recording device 1160. A secondexamining device (not shown) may be positioned along second conduit 1170between the bubble detector probe 76 and the inlet 1116 of thecontainment vessel 1110 to provide the practitioner access to the flowmaterial 1112.

[0205] In operation, flow is initiated by activating the pump 1120. Theflow rate of the flow material 1112 is permitted to stabilize beforeintroducing bubbles to the system 1105. Once the system 1105 hasstabilized, bubbles are introduced to the flow material 1112 byactivating the bubble-forming device 1143. The system 1105 is permittedto stabilize once again before calibrating the bubble detector 74.

[0206] The microbubble resolution of the bubble detector 74 may bedetermined by introducing bubbles of successively smaller diameters insuccessive tests. The macrobubble resolution of the bubble detector 74may be determined in a similar manner by introducing bubbles ofsuccessively larger diameters in successive tests. Once the rate ofbubble generation and flow rate have stabilized, the recording device1160 is activated to record the rate of bubble generation and the sizeof the bubbles generated. The bubble detector 74 to be evaluated isactivated for a predetermined amount of time.

[0207] The probe 76 examines the bubbles which are generally of knownsize and quantity, and the probe 76 delivers corresponding signals tothe bubble detector 74. The size and quantity of bubbles recorded by thebubble detector 74 are compared to the size and quantity of the bubblesrecorded by the recording device 1160. Typically, such comparison isperformed at a plurality of signal strengths and bubble sizes.Thereafter, one skilled in the art of mathematics may graphicallyrepresent this relationship and extrapolate the projected signalstrengths at a plurality of bubble sizes. When the signal-to-bubble sizerelation is graphically plotted, one skilled in the art of mathematicscan calculate one or more calibration constants based on the fit of thesignal strength to bubble size relationship. The calibration constant(s)can be programmed into the bubble detector 74 to calibrate the bubbledetector 74.

[0208] An alternative embodiment of the calibration and evaluationsystem 1105 is identical to the previously described system except forthe incorporation of a pulse dampener 1180, as illustrated in FIG. 59.The pulse dampener 1180 reduces or eliminates pressure oscillationsproduced by the pump 1120. Relatively large bubbles that may be producedby such pressure oscillations become trapped within the pulse dampener1180 so that they do not disturb the controlled formation of bubbles bythe bubble-forming device 1143.

[0209] As shown with further reference to FIG. 60, the pulse dampener1180 comprises a vessel body 1181 having an inlet 1182 and an outlet1184. The inlet 1182 is coupled in the first conduit 1130 between thepump 1120 and the connecting device 1140. The pump 1120 forces the flowmaterial 1112 into the vessel body 1181 through the inlet 1182. Thepressure exerted by the pump 1120 is maintained within the vessel body1181, thus forcing the flow material 1112 through the outlet 1184. Thus,any bubbles produced by the pump 1120 are trapped prior to reaching theconnecting device 1140.

[0210] While the invention may be susceptible to various modificationsand alternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

What is claimed is:
 1. A system for enriching a bodily fluid with a gas,the system comprising: a pump system adapted to transmit a bodily fluidfrom a patient; a gas-enriching device operatively coupled to the pumpsystem to receive the bodily fluid, the gas-enriching device combiningthe bodily fluid with a gas to form a gas-enriched bodily fluid; abubble detector arranged to detect bubbles in the gas-enriched bodilyfluid; and a controller adapted to control the pump system and thegas-enriching device automatically.
 2. The system, as set forth in claim1, wherein the pump system comprises: a pump adapted to pump the bodilyfluid through a tube; and a flow meter adapted to sense flow of thebodily fluid through the tube, the flow meter generating an actual flowrate signal correlative to flow through the tube, wherein the controlleris operatively coupled to the pump and to the flow meter, the controlleradapted to receive the actual flow rate signal and to control the pumpto maintain a desired rate of flow through the tube.
 3. The system, asset forth in claim 2, wherein the pump comprises: a peristaltic pump. 4.The system, as set forth in claim 2, wherein the flow meter comprises: aflow transducer adapted to be operatively coupled to the tube, the flowtransducer adapted to deliver to the flow meter a flow signalcorrelative to flow through the tube.
 5. The system, as set forth inclaim 2, comprising: a flow setting device operatively coupled to thepump to set the desired rate of flow through the tube.
 6. The system, asset forth in claim 5, wherein the flow setting device comprises: adisplay illustrating the desired flow rate; and a user-actuatable inputoperatively coupled to the display to adjust the desired flow rateillustrated by the display.
 7. The system, as set forth in claim 5,wherein the flow setting device comprises: a personality module having amemory adapted to store the desired flow rate and to deliver the desiredflow rate signal to the controller.
 8. The system, as set forth in claim7, wherein the desired flow rate stored in the personality modulecomprises a desired range of flow rates.
 9. The system, as set forth inclaim 1, wherein the gas-enriching device comprises a disposablecartridge adapted to be placed in an enclosure.
 10. The system, as setforth in claim 9, wherein the cartridge comprises: a housing; anenrichment device disposed in the housing to form a gas-enrichedphysiologic fluid; and a mixing device disposed in the housing to mixthe gas-enriched physiologic fluid with the bodily fluid to form thegas-enriched bodily fluid.
 11. The system, as set forth in claim 10,wherein the enrichment device comprises: an atomizing chamber adapted toreceive the gas through a gas inlet; and an atomizer disposed within theatomizing chamber, the atomizer adapted to receive physiologic fluid andto atomize the physiologic fluid upon delivery into the atomizingchamber to form the gas-enriched physiologic fluid.
 12. The system, asset forth in claim 10, wherein the mixing device comprises: a mixingchamber having a fluid inlet and a fluid outlet; and a fluid deliverydevice disposed within the mixing chamber in a predeterminedrelationship with the fluid inlet, the fluid delivery device adapted toreceive the gas-enriched physiologic fluid from the atomizing chamberand to deliver the gas-enriched fluid into the mixing chamber to mixwith the bodily fluid entering the mixing chamber through the fluidinlet to form the gas-enriched bodily fluid.
 13. The system, as setforth in claim 10, wherein the cartridge comprises: a fluid supplydevice disposed in the housing to supply a physiologic fluid to theenrichment device.
 14. The system, as set forth in claim 13, wherein thefluid supply device comprises: a fluid supply chamber having a fluidinlet and a fluid outlet; and a pump disposed within the fluid supplychamber, the pump adapted to draw a physiologic fluid into the fluidsupply chamber through the fluid inlet in the fluid supply chamber andto deliver the physiologic fluid to the enrichment device through thefluid outlet in the fluid supply chamber.
 15. The system, as set forthin claim 13, wherein the cartridge comprises: a valve assembly disposedin the housing, the valve assembly having valves to control flow of thephysiologic fluid between the fluid supply device and the enrichmentdevice and to control flow of the gas-enriched physiologic fluid betweenthe enrichment device and the mixing device.
 16. The system, as setforth in claim 10, wherein the enclosure comprises: a receiving chambersized to accept the cartridge therein; a first level sensor arranged todetermine fluid level in the enrichment device; a second level sensorarranged to determine a low fluid level in the mixing device; and athird level sensor arranged to determine a high fluid level in themixing device.
 17. The system, as set forth in claim 15, wherein theenclosure comprises: a receiving chamber sized to accept the cartridgetherein; and a valve actuation assembly adapted to actuate the valves ofthe valve assembly.
 18. The system, as set forth in claim 9, wherein theenclosure comprises: a door having a lock to secure the cartridge withinthe enclosure.
 19. The system, as set forth in claim 1, wherein thebubble detector comprises: an ultrasonic transducer pair comprising atransmitting transducer and a receiving transducer, the ultrasonictransducer pair being positionable to sense bubbles in a fluid flow; atransducer driver operatively coupled to the transmitting transducer tocause the transmitting transducer to deliver a pulsed ultrasonic signalacross the fluid flow to the receiving transducer; a signal conditioneroperatively coupled to the receiving transducer to receive the pulsedultrasonic signal from the receiving transducer, the signal conditionerconditioning the pulsed ultrasonic signal to produce a conditionedsignal; and a signal processor operatively coupled to the signalconditioner to receive the conditioned signal, the signal processordetermining information correlative to bubbles in the fluid flow inresponse to the conditioned signal.
 20. The system, as set forth inclaim 19, wherein the pulsed ultrasonic signal delivered by thetransmitting transducer comprises a frequency range of 3 MHz to 4 MHzand a pulse rate of about 3 KHz to 40 KHz.
 21. The system, as set forthin claim 19, wherein the signal conditioner comprises: a detectoradapted to detect the amount of ultrasonic energy of the pulsedultrasonic signal received by the receiving transducer.
 22. The system,as set forth in claim 19, wherein the signal conditioner comprises: ananalog-to-digital converter adapted to convert the amount of ultrasonicenergy detected by the detector into a digital signal.
 23. The system,as set forth in claim 19, wherein the signal processor comprises abuffer adapted to hold multiple digital signals.
 24. The system, as setforth in claim 23, wherein a reduction in the digital signal as comparedto previously recorded digital signals or an average of previouslyrecorded digital signals is correlative to bubbles in the fluid flow.25. The system, as set forth in claim 19, wherein the signal processorcomprises a digital signal processor.
 26. The system, as set forth inclaim 25, wherein the digital signal processor is adapted to detect andcount each bubble in the fluid flow.
 27. The system, as set forth inclaim 25, wherein the digital signal processor determines the volume ofeach bubble in the fluid flow.
 28. The system, as set forth in claim 27,wherein the digital signal processor converts the volume of each bubblein the fluid flow to a volume of each bubble when it reaches a patient.29. The system, as set forth in claim 25, wherein the digital signalprocessor determines an accumulated volume of bubbles in the fluid flowover a given period of time.
 30. The system, as set forth in claim 29,wherein the signal processor initiates the stop signal in response tothe accumulated volume of bubbles exceeding a predetermined limit, thestop signal being delivered to the controller to cause the controller tocease operation of the pump system and the gas-enriching device.
 31. Thesystem, as set forth in claim 1, wherein the controller comprises: afirst sensor assembly arranged to monitor the pump system, the firstsensor assembly delivering at least one first signal correlative tooperation of the pump system; a second sensor assembly arranged tomonitor the gas-enriching device, the second sensor assembly deliveringat least one second signal correlative to operation of the gas-enrichingdevice; a signal processor operatively coupled to the first sensorassembly and to the second sensor assembly to receive the at least onefirst signal and the at least one second signal, the signal processordelivering at least one pump system control signal in response to the atleast one first signal, the pump system adjusting its operation inresponse to receiving the at least one pump system control signal fromthe signal processor, and the signal processor delivering at least onegas-enrichment control signal in response to the at least one secondsignal; and an actuation assembly arranged to adjust operation of thegas-enriching device in response to receiving the at least onegas-enrichment signal from the signal processor.
 32. The system, as setforth in claim 31, wherein the first sensor assembly comprises: a flowtransducer adapted to be operatively coupled to a tube carrying thebodily fluid, wherein the at least one first signal comprises a flowsignal delivered from the flow transducer, the flow signal beingcorrelative to flow through the tube.
 33. The system, as set forth inclaim 32, wherein the signal processor comprises a comparison deviceadapted to receive the flow signal and to compare the flow through thetube to the desired flow range.
 34. The system, as set forth in claim33, wherein the signal processor delivers an enable signal to the pumpsystem in response to the flow signal being indicative of flow throughthe tube being within a desired flow range.
 35. The system, as set forthin claim 33, wherein the signal processor delivers a disable signal tothe pump system in response to the flow signal being indicative of flowthrough the tube being outside the desired flow range.
 36. The system,as set forth in claim 33, comprising: a first clamp adapted to beoperatively coupled to a draw side of the tube; and a second clampadapted to be operatively coupled to a return side of the tube, whereinthe signal processor closes the first clamp and the second clamp inresponse to the flow signal being outside the desired flow range. 37.The system, as set forth in claim 31, wherein the gas-enriching devicecomprises a cartridge adapted to be disposed in an enclosure, whereinthe cartridge comprises: a housing; a fluid supply device disposed inthe housing to supply a physiologic fluid; an enrichment device disposedin the housing and operatively couple to receive the physiologic fluidfrom the fluid supply device, the enrichment device converting thephysiologic fluid to a gas-enriched physiologic fluid; a mixing devicedisposed in the housing and operatively coupled to receive thegas-enriched physiologic fluid from the enrichment device and to receivethe bodily fluid from the pump system, the mixing device adapted to mixthe gas-enriched physiologic fluid with the bodily fluid to form thegas-enriched bodily fluid; and a valve assembly disposed in the housing,the valve assembly having valves to control flow of the physiologicfluid between the fluid supply device and the enrichment device and tocontrol flow of the gas-enriched physiologic fluid between theenrichment device and the mixing device; and wherein the second sensorassembly comprises: a transducer arranged to determine physiologic fluidsupplied by the fluid supply device; a first level sensor arranged todetermine fluid level in the enrichment device; a second level sensorarranged to determine a low fluid level in the mixing device; and athird level sensor arranged to determine a high fluid level in themixing device; and wherein the actuation assembly comprises: a valveactuation assembly disposed in the enclosure and adapted to actuate thevalves of the valve assembly.
 38. A method of enriching a bodily fluidwith a gas, the method comprising the acts of: (a) supplying aphysiologic fluid tp a cartridge; (b) enriching the physiologic fluidwith a gas in the cartridge to form a gas-enriched physiologic fluid;and (c) mixing the gas-enriched physiologic fluid with a bodily fluid inthe cartridge to form a gas-enriched bodily fluid.
 39. The method, asset forth in claim 38, wherein act (a) comprises the act of:pressurizing the physiologic fluid within the fluid supply chamber ofthe cartridge.
 40. The method, as set forth in claim 39, wherein the actof pressurizing comprises the act of: forcing a piston against thephysiologic fluid within the fluid supply chamber.
 41. The method, asset forth in claim 38, wherein act (b) comprises the act of: atomizingthe physiologic fluid within an atomization chamber of the cartridge.42. The method, as set forth in claim 41, wherein act (b) comprises theact of: transferring the physiologic fluid from a fluid supply chamberof the cartridge to the atomization chamber.
 43. The method, as setforth in claim 38, wherein act (c) comprises the act of: transferringthe gas-enriched physiologic fluid into a mixing chamber of thecartridge in a substantially bubble-free manner.
 44. The method, as setforth in claim 43, wherein the act of transferring comprises the act of:passing the gas-enriched physiologic fluid through a capillary.
 45. Amethod of operating an extracorporeal circuit, the method comprising theacts of: (a) loading a cartridge into an enclosure; (b) priming thecartridge with a physiologic solution; (c) priming the cartridge with abodily fluid; (d) enriching the physiologic solution with a gas to forma gas-enriched physiologic fluid; (e) mixing the gas-enrichedphysiologic fluid with the bodily fluid to form a gas-enriched bodilyfluid; and (f) delivering the gas-enriched bodily fluid to a patient.46. The method, as set forth in claim 45, wherein act (a) comprises theact of: retracting valve actuation pins within the enclosure prior toplacing the cartridge within the enclosure.
 47. The method, as set forthin claim 46, wherein act (a) comprises the act of: extending the valveactuation pins after placing the cartridge within the enclosure.
 48. Themethod, as set forth in claim 46, wherein act (a) comprises the act of:locking the cartridge within the enclosure.
 49. The method, as set forthin claim 45, wherein act (b) comprises the act of: pressurizing thephysiologic solution.
 50. The method, as set forth in claim 46, whereinact (b) comprises the acts of: drawing the physiologic solution into afluid supply chamber of the cartridge; pumping the physiologic solutionfrom the fluid supply chamber into an atomization chamber of thecartridge; and supplying the gas to the atomization chamber.
 51. Themethod, as set forth in claim 45, wherein act (c) comprises the acts of:opening a clamp on a draw side of a tube carrying the bodily fluid;pumping the bodily fluid into a mixing chamber of the cartridge untilthe bodily fluid reaches a predetermined level within the mixingchamber; and opening a clamp on a return side of the tube.
 52. Themethod, as set forth in claim 45, wherein act (d) comprises the act of:atomizing the physiologic fluid within an atomization chamber of thecartridge.
 53. The method, as set forth in claim 52, wherein act (d)comprises the act of: coupling a supply of the gas to the atomizationchamber.
 54. The method, as set forth in claim 53, wherein act (d)comprises the act of: transferring the physiologic fluid from a fluidsupply chamber of the cartridge to the atomization chamber.
 55. Themethod, as set forth in claim 45, wherein act (e) comprises the act of:transferring the gas-enriched physiologic fluid into a mixing chamber ofthe cartridge in a substantially bubble-free manner.
 56. The method, asset forth in claim 55, wherein the act of transferring comprises the actof: passing the gas-enriched physiologic fluid through a capillary. 57.The method, as set forth in claim 45, wherein act (f) comprises the actof: passing the gas-enriched bodily fluid through a catheter.
 58. Anautomated blood pump circuit comprising: a blood pump adapted to pumpblood through a tube; a flow meter adapted to sense blood flow throughthe tube, the flow meter generating an actual flow rate signalcorrelative to blood flow through the tube; and a controller operativelycoupled to the blood pump and to the flow meter, the controller adaptedto receive the actual flow rate signal and to control the blood pump tomaintain a desired rate of blood flow through the tube.
 59. The circuit,as set forth in claim 58, wherein the blood pump comprises: aperistaltic pump.
 60. The circuit, as set forth in claim 58, wherein theflow meter comprises: a flow transducer adapted to be operativelycoupled to the tube, the flow transducer adapted to deliver to the flowmeter a flow signal correlative to blood flow through the tube.
 61. Thecircuit, as set forth in claim 58, comprising: a flow setting deviceoperatively coupled to the blood pump to set a desired rate of bloodflow through the tube.
 62. The circuit, as set forth in claim 61,wherein the flow setting device delivers a desired flow rate signal tothe controller, and wherein the controller automatically adjusts theactual rate of flow through the tube to the desired flow rate inresponse to the desired flow rate signal and the actual flow ratesignal.
 63. The circuit, as set forth in claim 62, wherein the flowsetting device comprises: a display adapted to generate the desired flowrate signal correlative to the desired rate of blood flow through thetube.
 64. The circuit, as set forth in claim 63, wherein the displaycomprises: a digital panel illustrating the desired flow rate; and auser-actuatable input operatively coupled to the digital panel to adjustthe desired flow rate illustrated by the digital panel.
 65. The circuit,as set forth in claim 62, wherein the flow setting device comprises: apersonality module having a memory adapted to store the desired flowrate and to deliver the desired flow rate signal to the controller. 66.The circuit, as set forth in claim 65, wherein the desired flow ratestored in the personality module comprises a desired range of flowrates.
 67. The circuit, as set forth in claim 61, wherein the tube has adraw portion for drawing blood from a patient and a return portion forreturning blood to a patient, the circuit comprising: a draw tube clampoperatively coupled to the draw portion of the tube, the draw tube clampbeing moveable between a clamped position and an unclamped position; areturn tube clamp operatively coupled to the return portion of the tube,the return tube clamp being moveable between a clamped position and anunclamped position; and wherein the controller is operatively coupled tothe draw tube clamp and the return tube clamp, the controller adapted tomove the draw tube clamp and the return tube clamp between therespective clamped and unclamped positions.
 68. The circuit, as setforth in claim 67, wherein the blood pump circuit comprises: anextracorporeal circuit.
 69. A method of priming a blood pump circuit,the circuit having a tube having a draw portion for drawing blood from apatient and having a return portion for returning blood to a patient,the method comprising the acts of: (a) positioning the draw portion ofthe tube within a draw tube clamp; (b) positioning the return portion ofthe tube within a return tube clamp; (c) closing the draw tube clamp andthe return tube clamp; (d) opening the draw tube clamp; (e) pumpingblood through the draw portion of the tube and into a mixing reservoir;(f) opening the return tube clamp; and (g) pumping blood from the mixingreservoir through the return portion of the tube.
 70. The method, as setforth in claim 69, wherein act (c) comprises the acts of: delivering adraw tube clamp signal to the draw tube clamp; and delivering a returntube clamp signal to the return tube clamp.
 71. The method, as set forthin claim 69, wherein act (d) comprises the act of: delivering a drawtube unclamp signal to the draw tube clamp in response to receiving aprime signal.
 72. The method, as set forth in claim 69, wherein act (e)comprises the act of: enabling a pump in response to receiving a primesignal.
 73. The method, as set forth in claim 69, wherein act (f)comprises the act of: delivering a return tube unclamp signal to thereturn tube clamp in response to blood in the mixing reservoir reachinga desired level.
 74. The method, as set forth in claim 69, comprising:continuing to perform acts (e) and (g) until a stop signal is received.75. The method, as set forth in claim 74, comprising the act of:generating the stop signal in response to blood flow rate through thetube dropping below a minimum blood flow rate.
 76. The method, as setforth in claim 74, comprising the act of: generating the stop signal inresponse to actuation of a stop switch.
 77. The method, as set forth inclaim 69, comprising the act of: closing a vent valve of the mixingreservoir when the return tube clamp is opened.
 78. A method ofoperating a blood pump circuit, the circuit having a tube having a drawportion for drawing blood from a patient and having a return portion forreturning blood to a patient, the method comprising the acts of: (a)pumping blood through the draw portion of the tube and into a mixingreservoir; (b) mixing the blood within the mixing reservoir with agas-enriched physiologic fluid to form gas-enriched blood; (c) pumpingthe gas-enriched blood from the mixing reservoir through the returnportion of the tube; (d) generating an actual flow rate signalcorrelative to a rate of flow through the tube; and (e) automaticallycontrolling the rate of flow through the tube in response to the actualflow rate signal.
 79. The method, as set forth in claim 78, wherein act(a) comprises the act of: maintaining a fluid level within the mixingreservoir within a desired range.
 80. The method, as set forth in claim78, wherein act (b) comprises the act of: mixing the blood with agas-supersaturated physiologic fluid.
 81. The method, as set forth inclaim 78, wherein act (b) comprises the act of: mixing the blood with anoxygen-enriched physiologic fluid.
 82. The method, as set forth in claim78, wherein act (b) comprises the act of: mixing the blood with anoxygen-supersaturated physiologic fluid.
 83. The method, as set forth inclaim 78, comprising: continuing to perform acts (a), (b), and (c) untila stop signal is received.
 84. The method, as set forth in claim 83,comprising the act of: generating the stop signal in response to theflow rate through the tube dropping below a minimum flow rate.
 85. Themethod, as set forth in claim 83, comprising the act of: generating thestop signal in response to actuation of a stop switch.
 86. The method,as set forth in claim 78, wherein act (d) comprises the act of:operatively coupling a flow transducer to the tube, the flow transducergenerating the actual flow rate signal; and delivering the actual flowrate signal to a flow meter.
 87. The method, as set forth in claim 78,wherein act (e) comprises the act of: generating a desired flow ratesignal correlative to a desired flow rate through the tube; andautomatically adjusting the actual rate of flow through the tube to thedesired flow rate in response to the desired flow rate signal and theactual flow rate signal.
 88. A method of operating a blood pump circuit,the circuit having a tube having a draw portion for drawing blood from apatient and having a return portion for returning blood to a patient,the method comprising the acts of: (a) pumping blood through the drawportion of the tube and into a mixing reservoir; (b) mixing the bloodwithin the mixing chamber with a gas-enriched physiologic fluid to formgas-enriched blood; (c) pumping the gas-enriched blood from the mixingreservoir through the return portion of the tube; (d) generating adesired flow rate signal correlative to a desired rate of flow throughthe tube; (e) generating an actual flow rate signal correlative to anactual rate of flow through the tube; and (f) automatically adjustingthe actual rate of flow through the tube to the desired flow rate inresponse to the desired flow rate signal and the actual flow ratesignal.
 89. The method, as set forth in claim 88, wherein act (a)comprises the act of: maintaining a fluid level within the mixingreservoir within a desired range.
 90. The method, as set forth in claim88, wherein act (b) comprises the act of: mixing the blood with thegas-enriched physiologic fluid which comprises a gas-supersaturatedphysiologic fluid.
 91. The method, as set forth in claim 88, wherein act(b) comprises the act of: mixing the blood with the gas-enrichedphysiologic fluid which comprises an oxygen-enriched physiologic fluid.92. The method, as set forth in claim 88, wherein act (b) comprises theact of: mixing the blood with the gas-enriched physiologic fluid whichcomprises an oxygen-supersaturated physiologic fluid.
 93. The method, asset forth in claim 88, comprising: continuing to perform acts (a), (b),and (c) until a stop signal is received.
 94. The method, as set forth inclaim 93, comprising the act of: generating the stop signal in responseto the flow rate through the tube dropping below a minimum flow rate.95. The method, as set forth in claim 93, comprising the act of:generating the stop signal in response to actuation of a stop switch.96. The method, as set forth in claim 88, wherein act (d) comprises theact of: actuating a user-actuatable input operatively coupled to adisplay to adjust the desired flow rate illustrated by the display. 97.The method, as set forth in claim 88, wherein act (d) comprises the actof: storing the desired rate of flow in a memory of a personalitymodule, the personality module generating the desired flow rate signal.98. The method, as set forth in claim 97, wherein the desired flow ratestored in the personality module comprises a desired range of flowrates.
 99. The method, as set forth in claim 88, wherein act (e)comprises the act of: operatively coupling a flow transducer to thetube, the flow transducer generating the actual flow rate signal; anddelivering the actual flow rate signal to a flow meter.